GAMSAT Biology Mitosis and the Cell Cycle

Re: GAMSAT Biology Mitosis and the Cell Cycle

Binary Fission
Bacteria divide by a process known as binary fission. The process involves the migration of two identical DNA molecules to opposite ends of the cell. The cell then divides in two and each new cell enlarges to the original size. DNA replication proceeds bidirectionally from the origin to a specific termination site.

The doubling time of bacteria in the presence of unlimited resources can be calculated as follows:

b = B x 2ⁿ

b is the number of bacteria at the end of the time interval; B is the number of bacteria at the beginning of the time interval; n is the number of generations.

Eukaryotic cell cycle
The eukaryotic cell cycle is divided into 5 different phases.
Gap 1 (G₁)
Synthesis (S)
Gap 2 (G₂)
Mitosis
Cytokinesis (C)
G₁, S, G₂ = collectively called interphase.
Mitosis and cytokinesis = collectively called M phase.

The following image shows the different phases of the eukaryotic cell cycle:

Interphase
Interphase takes place for the preparation of mitosis. G₁, S and G₂ are subphases of interphase. G₁ is the primary growth phase. DNA synthesis occurs in the S phase. The G₂ phase occurs before mitosis and after the S phase.

M Phase
The M phase contains mitosis and cytokinesis and occurs after the G₂ phase. Mitosis can be divided into 5 stages – prophase, prometaphase, metaphase, anaphase, telophase, Cytokinesis then occurs.

The DNA has been replicated after G₂ phase.

Prophase: chromosomes condense and become visible. Chromosomes are seen as two sister chromatids and are held together by a centromere. Spindles begin to form.

Prometaphase: chromosomes attach to microtubules and chromosomes move to the equator of the cell.

Metaphase: chromosomes are aligned along the center of the cell in a straight line. The equator of the cell is called the metaphase plate.

Anaphase: centromeres of sister chromatids are degraded and individual chromosomes are freed. Chromosomes move to opposite poles and spindle poles move apart.

Telophase: the clustered chromosomes at each pole decondense. Nuclear envelopes form around the chromosomes.

Cytokinesis divides the cell into two separate cells.

The cell cycle can be halted at 3 different checkpoints. The checkpoints include:
1. G1/S – commitment to divide.
2. G2/M – important to ensure the integrity of DNA.
3. Spindle checkpoint – ensures all chromosomes are attached to the spindle fibers.

GAMSAT General Chemistry Atoms and Molecules

Re: GAMSAT General Chemistry Atoms and Molecules

Atoms

Atoms are the basic building blocks of all matter. Each atom is composed of a nucleus. The nucleus contains protons and neutrons and is surrounded by one or more electrons.

Protons have a positive charge.
Electrons have a negative charge.
Neutrons are electrically neutral.

Electrons and protons have opposite charges of equal magnitude. The size of a proton and neutron are approximately equal, however an electron is much smaller.

Elements

An element is a chemical substance containing atoms that have the same number of protons in their atomic nuclei. Elements are the building blocks of all compounds. Elements are displayed as follows:

A is the mass number of the element. This is the number of protons plus neutrons in the nucleus.

Z is the atomic number. This is the number of protons in the nucleus.

An element is characterized by the number of protons it has. Any element can only have one number of protons. However, the number of neutrons or electrons can change and the element will still retain its identity.

If there are two atoms of the same element that have a different mass number (different number of neutrons) these are said to be isotopes.

Three isotopes of carbon include:

¹²C, ¹³C and ¹⁴C.

Each isotope of carbon contains 6 protons (giving the element its identity as carbon). ¹²C contains 6 neutrons, ¹³C contains 7 neutrons, and ¹⁴C contains 8 neutrons.

The atomic weight or molar mass (M) of an atom is given in atomic mass units (amu). The amu is a ratio and is defined by carbon-12. One atom of ¹²C has an atomic weight or molar mass of 12 amu. All other atomic weights are measured against this standard.

¹²C is also used to define a mole. A mole is the number of carbon atoms in 12 grams of ¹²C.
Avogadro’s number also defines the number of carbon atoms in 12 grams of carbon as 6.022 x 10²³.

So there are 6.022 x 10²³ carbon atoms in 12 grams of 12C.

The formula that surrounds these concepts is as follows:

n = moles

m = mass in grams

M = molar mass (found on periodic table for individual atoms)

The Periodic Table
All elements are listed on the periodic table. Elements are listed based on their atomic number from left to right. The vertical columns of the periodic table are called groups and the horizontal rows are called periods.

Groups are numbered from 1 to 18 and periods are numbered from 1 to 7.

The periodic table above divides the elements into three sections:
– Metals are on the left (pink)

– Nonmetals are on the right (light green)

– Metalloids are along the darker green area that separates the metals and non-metals.

Nonmetals generally have lower melting points than metals and form negative ions. Molecular substances are usually made up from only nonmetals. E.g. H₂O.

Metals tend to lose electrons to form positive ions. All metals exist as solids at room temperature with the exception of mercury, which is a liquid.

The metals that range from group 3 to group 12 are known as transition metals.

Group 18 is known as the noble gases; group 17 is known as halogens; group 1 is known as alkali metals; group 2 is known as alkaline earth metals.

Group 1 elements form 1+ cations; group 2 elements form 2+ cations; group 14 elements can all form 4 covalent bonds with nonmetals; group 15 elements can form 3 covalent bonds; group 16 contains oxygen (important); group 17 elements (halogens) are very reactive, forming only 1 bond with other elements; group 18 elements (noble gases) are nonreactive.

Ions
An element becomes an ion when it has more or fewer electrons than protons. Negative ions are known as anions and positive ions are known as cations.

General rule: Metals form cations and non-metals form anions.

General predictions about elements can be made based on their position in the periodic table.

Atomic size: Atomic size (radius) increases as you move from right to left and from top to bottom. This is because when you move from left to right the effective nuclear charge increases (more protons), and each additional electron is pulled more strongly toward the nucleus. Atomic radius increases from the top to bottom because with each added shell the atom becomes larger. Note: As you move down the periodic table, each underlying period will have elements with an extra shell of electrons. E.g. helium has one shell and Lithium has two shells.

Ionisation energy: Ionisation energy is defined as the energy required to remove an electron from an atom. If an electron is more strongly attached to the nucleus it will require more energy to be removed. Ionisation energy increases from left to right and from bottom to top. When you move from left to right the elements have a greater nuclear charge (more protons). There are more protons that create a stronger attraction with the surrounding electrons and as a result more energy is required to remove the electron from the atom – greater ionization energy.

As you move down the periodic table the distance of the electron from the nucleus increases (more electron shells as you move down the periodic table). This increased distance creates a decrease in electric field strength and as a result less energy is required to remove an electron. This explains why the ionization energy increases as you move up the periodic table.

Electronegativity:
Electronegativity is the tendency of an atom to attract an electron in a bond that it shares with another atom. Electronegativity tends to increase as you move from left to right and from bottom to top.

Molecules
Atoms can be held together by bonds.

A covalent bond occurs when two electrons are shared by two nuclei. The electrons (negatively charged) are pulled toward both positively charged nuclei via electrostatic forces.

A compound is formed when a substance contains one or more elements in a definite ratio.

The empirical formula of a pure compound is the simplest whole number ratio between the number of atoms of the different elements in the compound. For example the empirical formula for glucose is CH₂O.

The molecular formula of a molecule states the exact number of the different atoms that make up the molecule. The molecule formula for glucose is C₆H₁₂O₆.

Naming inorganic compounds
In the GAMSAT it is uncommon that ACER will directly test the ability to name inorganic compounds. However it is important that candidates are able to identify compounds that are being referred to in the respective questions.

Ionic compounds are named after their cation and anion. When naming an ionic compound the cation name is placed in front of the anion name. For example NaCl is called sodium chloride.

Monoatomic anions and polyatomic anions are given the suffix –ide. For example H^– is a hydride ion and OH^– is a hydroxide ion.

Chemical Reactions and Equations
Compounds that initially react in a chemical reaction are termed reactants. Reactants are always written on the left hand side of the chemical equation. The compounds that are produced in the reaction are termed the products of the chemical reaction. Products are always written on the right hand side of the chemical equation.

2 HCl + 2 Na → 2 NaCl + H₂

The coefficients in the above equation represent the relative number of moles of reactants that combine to form the relative number of moles of products.

The law of conservation of mass states that the number of atoms of a given element remains constant during the process of a chemical reaction.

Types of Chemical Reactions
In terms of the GAMSAT students should be familiar with the four fundamental types of reactions:

Combination: C + D –> E

Decomposition: E –> C + D

Single Displacement: C + DE –> D + CE

Double Displacement: CD + EF –> CF + DE

The letters C, D, E and F represent hypothetical elements or molecules.

Oxidizing vs Reducing agents

The following must be memorized for the GAMSAT.

An oxidizing agent will cause oxidation to occur, whilst the agent itself will be reduced.
A reducing agent will cause reduction to occur, whilst the agent itself will be oxidized.

If something is reduced it gains electrons. If something is oxidized it loses electrons.

REMEMBER:
OIL RIG – Oxidation Is Loss; Reduction Is Gain

GAMSAT Study Plan – 1 week before the GAMSAT

Re: GAMSAT Study Plan

With GAMSAT just around the corner, it is important to get the last week of study right. You MUST replicate exam conditions so you can get the feel of what the actual exam will be like.

By sitting the practice exams under timed conditions you will get the feel for the speed in which you have to move through the exam. By completing the practice GAMSAT exams you will be able to identify your strengths and weaknesses, so you can breeze through the easy question topics in SIII and leave the more challenging questions to the end. With practice, you will be well prepared to write the two essays in the allocated time.

The following is a sample GAMSAT routine that can be followed 1 week before the GAMSAT.

G-7:
– Acer half exam – check solutions and note down incorrect answers
– 1-2 hours reading ‘The Meaning of Things by A.C. Grayling’ or ‘ 50 Big Ideas You Really Need to Know by Ben Dupré + taking notes of important ideas/quotes you can use for section II

G-6: 
– Acer full exam – check solutions and note down incorrect answers
– 1-2 hours reading above books + taking notes
– 5-10 sets of words from www.vocabulary.com (select MCAT word-list = closest to GAMSAT)

G-5:
– Acer half exam – check solutions and note down incorrect answers
– 1-2 hours reading above books + taking notes
– 5-10 comprehension practice units from www.readtheory.org

G-4:
– Acer full exam – check solutions and note down incorrect answers
– 1-2 hours reading above books + taking notes
– 5-10 sets of words from www.vocabulary.com

G-3:
– Attempt AceGAMSAT SIII Mock-Exam – check solutions and note down incorrect answers
– 1-2 hours reading above books + taking notes
– 5-10 sets of words from www.vocabulary.com
– 5-10 comprehension practice units from www.readtheory.org

G-2: 
– Go back and attempt all the questions that you marked as wrong in the previous exams. Check solutions again and make sure you know where you went wrong (important)
– Write 2 timed-essays using quotes from Random Quote Generator

G-1:
– Relax and Meditate
– Read topics from ‘The Meaning of Things’ and ’50 Big Ideas You Really Need to Know’ throughout the day

Sample Meditation!

Find a quiet comfortable place to sit. Sit upright on the ground with legs crossed. You can close your eyes, or you can look down at the ground. Start by focusing on your breath, taking slow, deep breaths. Remember to breath in through your nose and out through your mouth. Breath the surrounding air into your belly, not just your chest. Pace your breath: Breath in for 3 seconds and out for 3 seconds. During this process you will feel your thoughts and emotions settling down as you focus on your breath.

It also helps to have a quiet tune playing in the background. I recommend the following:

Meditation tune 1: Rose theme
Meditation tune 2: Braveheart theme

Be aware that as you attempt to quiet your mind, thoughts will still come in to pay a visit. Acknowledge them, then let them go, always returning your focus to your breath.
The aim of meditation is to clear your mind for the following exercises and allow you to have laser-focus on your priorities for the day.

G:
Day of the GAMSAT!

– Bring a jumper just in case.  Even if it’s 30 degrees plus outside, the air-conditioning can be very cold.

– Get enough sleep!  Sleep at least 8 hours the night before the GAMSAT.

– Do not bring any study notes to the exam. This will only cause stress. Simply relax before the exam.

– Arrive early – nothing is more stressful than worrying about being on time.

– Remember your pencils and invest in a good pen for section 2 (this is very important)

– Pack a nice morning tea and good lunch so you have something to look forward to. Include lots of low GI food for long-lasting energy. Good examples are: Chicken and salad sandwich on multigrain bread, yogurt, fruit and tuna.

– DO NOT nap in the afternoon in the weeks/days leading up to the exam. It is not good for your body to expect a nap at 3 in the afternoon – because you will be doing S3 at this time.

– Bring water in a clear bottle (label removed).

Preparation 1 month before GAMSAT

Re: Preparation 1 month before GAMSAT

Only 1 month until GAMSAT Australia 2016!

Now is the time to dig-deep into all of your practice materials.

If you have not already done so it is time to practice questions under timed conditions. Use one of the full Acer sample papers. Sit on a desk in a quiet room, switch your phone to airplane mode, and start your timer. Finish section 1 in one sitting. Have a 10 minute break and attempt the essay questions in section 2 under these timed conditions. Now go have a break and have something to eat and drink (low GI food and water).

When you’re ready (30 minutes – 1 hour) come back, start your timer and attempt section 3.
After completion, take a break, relax and then go through all the answers and see where you went wrong (this is very important! – NOTE: Acer has previously copied questions exactly from their practice papers and placed them into the real exam! These questions are EASY marks! And will give you more time to complete the rest of the exam).

If you have completed all Acer practice papers for section 3, here is a FREE S3 mock-exam you can go through – https://www.acegamsat.com/siii-mock-exam/

The more you can replicate the actual exam conditions the better!

You should be writing at least four essays per week starting from now and up until two days before the GAMSAT exam. Leave the day before the GAMSAT for relaxation and leave some time for meditation.

Goodluck!

GAMSAT Biology – Energy, Metabolism and Respiration

Re: GAMSAT Biology

Adenosine Triphosphate (ATP)
ATP is the source of energy used in cellular energy transactions. The chemical bonds in ATP are important for the storage and release of energy. An enzyme removes a phosphate group from ATP and energy is released. This energy is used in cellular reactions.

Cellular Metabolism
Metabolism is the total of all chemical reactions carried out by an organism. There are two types of reactions:

Catabolism: Reactions that produce energy by breaking down molecules.

Anabolism: Reactions that use energy to build up molecules.

There are 3 basic stages of metabolism. These include:

1. Macromolecules are broken down into their constituent parts. E.g. proteins, lipids and polysaccharides are broken down into amino acids, fatty acids and monosaccharides respectively.
2. These constituent parts are oxidized to produce acetyl CoA, pyruvate and other metabolites. During this process some ATP is formed, along with NADH and FADH₂. This process does not directly use oxygen.
3. If oxygen is present and the cell can utilize this oxygen, the metabolites formed (stage 2) can go into the citric acid cycle and oxidative phosphorylation will take place to form large amounts of energy (ATP, NADH, or FADH₂).

Stages 1 and 2 both produce energy. These stages are called respiration. If no oxygen is used the respiration is anaerobic. If oxygen is used the respiration is aerobic.

Glycolysis
Glycolysis is the first stage of anaerobic and aerobic respiration. Glycolysis involves breaking down a 6-carbon glucose molecule into two 3-carbon pyruvate molecules. Glycolysis will occur in the presence or absence of oxygen. The reactions of glycolysis occur in the cytosol of the cell. Overall 2 ATPs are used and 4 ATPs are produced. Two pyruvate molecules and 2 NADH molecules remain at the end of glycolysis.

Glycolysis is best learnt visually (above video) so students can see the process occurring in the cell.

Aerobic Respiration
If oxygen is present in a cell that can undergo aerobic respiration, the products of glycolysis (NADH and pyruvate) will move into the matrix of a mitochondrion. The NADH and pyruvate will diffuse (facilitated diffusion) through the outer membrane. The pyruvate diffuses into the matrix and is converted to acetyl CoA in a reaction that produces CO₂ and NADH.

Krebs Cycle (Citric Acid cycle)
Acetyl CoA is a coenzyme, which transfers two carbons from pyruvate to oxaloacetic acid to initiate the Krebs cycle. Each turn of the Krebs cycle produces 1 ATP, 3 NADH and 1 FADH₂. During each cycle two carbon atoms are lost as CO₂.

Amino acids can be deaminated and converted to pyruvic acid or acetyl CoA. Fatty acids can be converted to acetyl CoA. The acetyl CoA is responsible for the initiation of the Krebs cycle.

The process of producing ATP in the Krebs cycle (citric acid cycle) is termed substrate-level phosphorylation.

Detailed knowledge of each step of the Krebs cycle is not required for the GAMSAT.

Electron Transport Chain
The electron transport chain is a series of proteins in the inner membrane of the mitochondrion. Electrons from NADH and FADH₂ are passed through the series of proteins and are accepted by oxygen to form water. As these electrons are passed through the protein series, protons are pumped into the intermembrane space. This creates a proton gradient, which is termed the proton-motive force. This proton-motive force moves protons through ATP synthase to produce ATP.

2-3 ATP molecules are produced from each NADH and 2 ATP molecules are produced from FADH₂.

The overall products and reactants for respiration are:
Glucose + O₂ à CO₂ + H₂O

Enzymes
Enzymes are biological catalysts that lower the activation energy of a reaction. A lower activation energy results in the reaction proceeding more quickly than without an enzyme present. The enzyme itself is not changed or consumed in the reaction, so only a small amount of enzyme is needed and it can be recycled.

Enzymes contain active sites that conform to fit the shape of substrates. This allows for the substrate to bind to the active site of the enzyme. Most enzymes are proteins.

Enzyme function can be affected by environmental factors. The rate of an enzyme-catalyzed reaction is affected by the concentration of the reaction substrate and enzymes. Chemical and physical factors can alter the three-dimensional shape of the enzyme, which can affect the ability of the enzyme to catalyse the reaction. These factors include temperature, pH and the presence of regulatory molecules.

Temperature
The rate of an enzyme catalysed reaction increases with increasing temperature, but only until it reaches a certain temperature called the optimum temperature. At temperatures above the optimum temperature the enzyme will denature and loss functionality.
The optimum temperature of an enzyme usually corresponds to the temperature in which it is found in the body.

pH
Most enzymes have an optimum pH that ranges from a pH of 6-8. Enzymes that are not at their optimal pH will function with decreased efficiency and may even become denatured.

Inhibitors and activators
Different substances can bind to enzymes and alter their shape. An inhibitor is a substance that can bind to an enzyme and decrease its activity. There are two types of enzyme inhibition.

Competitive inhibition: Inhibitors compete with the substrate for the same active site on the enzyme.

Non-competitive inhibition: Inhibitors bind to a location other than the active site. This changes the shape of the enzyme and it will not be able to bind to the substrate.

An allosteric activator binds to allosteric sites in the enzyme. This keeps the enzyme in its active configuration and increases the activity of the enzyme.

Enzyme cofactors
Cofactors are chemical components that assist in the functioning of enzymes. Cofactors are usually metals and coenzymes are organic molecules such as vitamins.

GAMSAT Physics Fluids and Solids

Re: GAMSAT Physics Fluids and Solids

A fluid is either a liquid or a gas. The molecules in a fluid are not arranged in any order or structure and thus move about in random directions relative to each other. The molecules of a fluid bond weakly, spin, and move past each other.

The molecules in solids are held in place by permanent molecular bonds. The molecules bond strongly and vibrate in a fixed position.

Density
Density (ρ) can be defined as the amount of mass (m) a fluid contains in a specified volume (V). It is defined as the ratio of its mass to its volume.

ρ = m/V

ρ = density, m = mass, V = volume

The units for density are Kg/m³
Students should know that density increases as you from gas to liquid to solid.

Density: solid > liquid > gas

Gases are the least dense and can be compressed, unlike solids and liquids, which for the GAMSAT are treated as incompressible.

Specific Gravity
Specific gravity is the ratio of the density of a substance to the density of water.

S.G. = ρ_substance/ρ_water

S.G. = specific gravity, ρ_substance = density of a substance, ρ_water = density of water

The following 4 points must be learnt for the GAMSAT:

1. The density of water is 1g/ml = 1g/cm³; 1g/cm³ is the same as 10³kg/m³

2. A specific gravity of less than one = substance lighter than water

3. A specific gravity of exactly one = substance equally as heavy as water

4. A specific gravity of more than one = substance heavier than water

We can use specific gravity of a substance to gain an intuitive understanding of the relative weight of the substance to water.

For example mercury has a specific gravity of 13.63, so lifting a container full of mercury will be equivalent to lifting 13.63 containers of water.

Pressure
Pressure problems arise in almost every GAMSAT exam. Pressure (P) can be defined as the force (F) per unit area (A):

P = F/A

F = perpendicular force to area in Newtons (N)

P = pressure in Pascal (Pa). 1 Pa = 1N/m²

A = area in square meters (m²)

Pressure can also be calculated as potential energy per unit volume. The following equation can be used to calculate different pressures in liquids at different depths. Pressure is calculated by multiplying density of fluid (ρ) with the acceleration due to gravity (g) and the depth below the surface of the fluid (h)

P = ρgh

P = pressure, ρ = density of fluid, g = acceleration due to gravity, h = depth below surface

It is important to understand the following characteristics of force and pressure of liquid fluids when solving these problems in the GAMSAT.

– At a certain depth, the pressure if the fluid is the same in all directions
– The shape or surface area of the container does not affect fluid pressure
– Fluids exert forces that are always at 90 degrees (perpendicular) to the surface of the container
– The pressure of a fluid is directly proportional to the density of the fluid and to its depth.

Buoyancy and Archimedes Principle
When an object is submerged in water (object replaces water) an upward force acts on the submerged object. This is termed the buoyant force.

Archimedes principle states that the buoyant force (F_b) is an upward force that acts on a submerged object, and is equal to the weight of fluid that is displaced by the submerged object.

The equation for the buoyant force is:

F_b = ρ_fluidVg

F_b = buoyant force, ρ_fluid = density of fluid, V = volume of fluid displaced, g = acceleration due to gravity

In previous years of the GAMSAT there have been questions that involve using the specific gravity of a fluid to determine the height of an object below or above the surface of the water.

The specific gravity of the fluid is equivalent to the height of an object partially submerged in the fluid.
If the specific gravity of the fluid is 0.5, then 50% of the height of the object will be immersed in the water and 50% of the height will be above the water. If specific gravity is 0.6, then 60% of the height will be immersed and 40% of the height will be above the water.

Fluids in Motion
Molecules of a moving fluid can be described as having two types of motion. These are laminar flow and turbulent flow.

Laminar flow is the fluid motion in which all the particles in the fluid are moving in a straight line. The particles within a layer are moving at the same rate and all particles are moving in the same direction.

Turbulent flow is an irregular flow of particles. Unlike the linear motion of laminar flow, the particles of turbulent flow move in a state of chaos, with some particles opposing the direction of others and causing collisions.

The rate of Laminar flow through a pipe can be determined by the following:
To determine the volume (V) past a point we multiply cross-sectional area (A) by length/distance (d).
Volume = (cross sectional area) x (distance)

Distance = (velocity) x (time)
d = vt

Therefore,
Volume = Avt
V = Avt

We have found the volume, now we can determine the rate (R):

Rate (R) is given by dividing the volume past a point by time.
R = (volume past a point) / time
R = Avt/t
R = Av

The continuity equation, which is used for a fluid in an enclosed tube can be written from the above equation:
A₁V₁ = A₂V₂
The subscripts 1 and 2 represent different points in the line of flow of a fluid.

Fluid Viscosity and Determination of Flow
Fluid velocity is defined as the resistance of fluid layers to flow past each other. The higher the viscosity of a fluid, the slower the fluid will flow. So if a fluid has a high viscosity coefficient (honey), it will flow slower than a fluid with a low viscosity constant (water).

Reynolds number (R) can be used to determine if the flow of a fluid is laminar or turbulent. The following equation is used:

R = vdρ/η

R = Reynolds number, v = velocity of flow, d = diameter of tube, ρ = density of fluid,
η = viscosity coefficient

When Reynolds number is less than 2000, flow in a pipe is generally laminar, and when greater than 2000, flow is generally turbulent.

Surface Tension
Surface tension can be defined as the intensity of intermolecular forces per unit length.

The surface tension of a liquid results from an imbalance of the cohesive forces between molecules:

1. A molecule in the bulk liquid experiences cohesive forces with other molecules in all directions.
2. A molecule at the surface of a liquid experiences only net inward cohesive forces.These cohesive forces between water molecules can allow some insects that are usually denser than water, to float and stride on the water surface.

Solids
Solids are elastic to some extent. They can change their dimensions by compressing or stretching, whilst maintaining their bonds.

Stress and strain are important concepts to understand when examining the elasticity of solids.

1. Stress is defined as the ratio of force applied to an object to the area over which the force is applied. The units for stress are N/m²
Stress = force/area

2. Strain is defined as the fractional change in dimension of an object caused by the stress. Strain has no units.

Stress and strain are proportional to each other, and this proportionality can be given as a ratio known as the modulus of elasticity (ME). To determine to modulus of elasticity, we simply divide the stress by the strain.
ME = stress/strain

GAMSAT Physics Translational Motion

Re: GAMSAT Physics Translational Motion

Scalars and Vectors
Knowing the difference between vectors and scalars will be advantageous when solving physics problems in the GAMSAT. A vector is a physical quantity that has both direction and magnitude; a scalar is a physical quantity that has magnitude but no direction.

Arrows can be used to reveal the direction of the vector. The length of the arrow will reveal the magnitude of the vector.

Adding and Subtracting Vectors
When adding vectors, the head of the first vector is placed to the tail of the second vector. An arrow is drawn from the tail of the first to the head of the second. The resulting arrow represents the vector sum of the other two vectors.

For the subtraction of vectors, place the heads of the two vectors together and draw an arrow from the tail of the first to the tail of the second. The resulting arrow represents the vector difference between the two vectors.

Resolution of Vectors and Trigonometric Functions
A vector can be divided into two components. These two components are perpendicular to each other. A vector is resolved into its scalar components. The lengths of the component vectors are found through Pythagoras Theorem and Trigonometric Ratios.

This skill is required in projectile motion problems in the GAMSAT. It is essential that students are able to understand and apply Pythagoras Theorem and Trigonometric Ratios.

Distance and Displacement
Distance and displacement are respectively scalar and vector components. Displacement is distance with an added dimension. This added dimension is direction.

Simply put, we can say that distance refers to how much ground an object has covered and displacement is the object’s overall change in position.

To test your understanding of this distinction, consider the motion depicted in the diagram below. A lady walks 4 meters East, 2 meters South, 4 meters West, and finally 2 meters North.

Even though the lady has walked a total distance of 12 meters, her displacement is 0 meters. During the course of her motion, she has “covered 12 meters of ground” (distance = 12 m). Yet when she is finished walking, she is not ‘out of place. In other words, there is no displacement for her motion (displacement = 0 m). Displacement, being a vector quantity, must give attention to direction. The 4 meters east cancels the 4 meters west; and the 2 meters south cancels the 2 meters north. Vector quantities such as displacement are direction aware. Scalar quantities such as distance are ignorant of direction. In determining the overall distance traveled by the lady, the various directions of motion can be ignored.

Speed and velocity
Speed and velocity are respectively scalar and vector components. Velocity is speed with the added dimension of direction. The units for velocity are expressed in length divided by time – e.g. meters/sec (m/s); feet/sec; miles/hour.

The following two equations must be memorised for the GAMSAT.

Speed = distance/time

Velocity = displacement/time

Acceleration
Acceleration is the rate of change in velocity. Acceleration is a vector, meaning that it has a direction and a magnitude. An object is accelerating if it is changing its velocity. The units for acceleration are expressed as velocity divided by time such as meters/sec².

When an object experiences negative acceleration it is termed deceleration.

The formula for acceleration must be memorised for the GAMSAT.

Acceleration = rate of change of velocity/time.

Uniformly Accelerated Motion
Uniformly accelerated motion is motion that involves constant acceleration. Constant acceleration means that both the magnitude and direction of acceleration must remain constant. A particle that exhibits uniform accelerated motion will always accelerate at a constant rate. When this particle is accelerating on a linear path, there are 4 variables that can describe its motion. These are:

Time (t) – scalar

Displacement (x) – vector

Velocity (v) – vector

Acceleration (a) – vector

Three basic equations can be used to derive the values of these variables. These equations are usually provided on the GAMSAT stimulus material, but they should be memorised for speed and efficiency. Manipulation of these equations will become second nature through repetition and practice.

The linear motion equations are as follows:
x = x_o + v_ot + 1/2at²
v = v_o + at
v² = v_o² + 2ax

When deciding which equation to use, choose the one for which you know the value of all but one of the variables.

Remember: constant acceleration and linear motion are required in order to use these equations.

Another important concept in the GAMSAT is average velocity. When an object experiences uniformly accelerated motion the average velocity can be determined using the following formula:
V_avg = ½(v + v_o)