A Level Physics (AQA)

What is breaking stress?

Refers to the stress which causes a material to break.

What is a brittle material?

Refers to an object that shows very little strain and extends very little before breaking, especially beyond the elastic limit.

What is the centre of mass?

Refers to the single point through which all the mass of an object acts.

What is the conservation of energy?

Refers to the principle which states that energy cannot be created or destroyed, only transferred or stored.

What is the conservation of momentum?

Refers to the principle where the total momentum before and after an event are equal, assuming no external forces act.

What is a couple?

Refers to 2 equal and opposite parallel forces that act on an object through different lines of action (are co-planar), which causes a rotation.

What is density?

Refers to the mass per unit volume of a material.

What is efficieny?

Refers to the ratio of useful output to total input in a given system.

What is elastic limit?

Refers to the force beyond which an object will no longer deform elastically and deform plastically.

What happens before the elastic limit?

The object is able to deform elastically.

What happens after the elastic limit?

The object is no longer able to return to its original shape and deforms plastically.

What is equilibrium?

Refers to when the resultant forces/moments on an object are equal to 0.

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What is a moment?

Refers to the product of a force and the perpendicular distance from the line of action of the force to the pivot/ Refers to the turning point of a force.

What is Newton’s First Law?

“An object will remain in its current state of motion, unless acted on by a resultant force. An object requires a resultant force to be able to accelerate.”

What is Newton’s Second Law? (Mommentum)

“The sum of the forces acting on an object is equal to the rate of change of momentum of the object.”

What is Newton’s Second Law?

“The magnitude of a resultant force of an object is direclty proportional to the acceleration of an object.”

What is Newton’s Third Law?

“If an object exerts a force on another object, then the other object must exert a force back, that is opposite in direction and equal in magnitude.”

What is a vector quantity?

A quantity with magnitude and direction.

What are some key examples of vector quantites?

1) Velocity
2) Displacement
3) Acceleration
4) Momentum
5) Force

What is a scalar quantity?

Refers to a quantity with only magnitude.

What are some examples of scalar quantities?

1) Speed
2) Distance
3) Mass
4) Energy
5) Temperature

What is tensile strain?

Refers to the ratio of an object’s extension to its original length.
(ΔL / L)

What is tensile stress?

Refers to the amount of force acting per unit area, which is measured in Pascals (Pa). [F/A]

What is terminal speed?

Refers to the maximum speed of an object that occurs when resistive and driving forces acting on the object are equal to eachother.

What is Young Modulus?

Refers to the ratio of stress to strain for a given material, which is measured in Pascals (Pa)

How do you find the RF from a scale diagram?

1) Resolve the forces into components and use Pythagoras to find the side.

2) Use a scale diagram and draw a parallelogram of forces to find the RF.

What is a plastic material?

Refers to when a material experiences a large amount of extension as the load is increased.

Why doesn’t the force–extension graph return to the origin after a material is stretched beyond its elastic limit?

The area between the loading and unloading gradient is the work done to permanently deforming the material, so the gradient of unloading the spring does not go through 0.

What are stress-strain graphs?

Refers to graphs which describe the behaviour of a material.

What do stress-strain graphs show in terms of points?

1) UTS (Ultimate tensile strength)
2) Elastic limit
3) Limit of proportionality
4) Breaking stress

What do stress-strain gradient graphs’ show?

Young Modulus

What does the area under stress-strain gradient graph’s show?

Elastic energy

What is the Young Modulus?

Refers to the value which describes the stiffness of a material.

How do you find the YM from a strain-stress graph?

Calculate the gradient of the graph.

What happens when a spring is stretched vertically?

Kinetic energy is converted into elastic strain energy as the force is applied, causing the spring to stretch.

What happens when a spring is released from the stretching force vertically?

Elastic energy is transferred back into kinetic energy, which is then transferred in to gravitational energy as the spring retracts.

What is momentum?

Refers to the product of an object’s mass and velocity.

What is an inelastic collision?

Refers to a collision where the total kinetic energy before and after the collision are not equal.

What is an elastic collision?

Refers to a collision where the total kinetic energy before and after the collision are the equal.

What is power?

Refers to the rate of energy transfer, measured in watts (W)

How do you find power?

P= W/T or P = E/T

How do you represent an inelastic collision as an equation?

ΔEk = Ek [final] - Ek [initial]

What is impulse?

Refers to a change of momentum of an object when a force acts on it, which is equal to the product of a force and the time taken for it to act. (Product of force and time)

How do you represent impulse as an equation?

F Δt = Δ(mv)

What is the area under a force time graph used to calculate?

Impulse

What is the gradient of a distance--time (d-t) graph used to calculate?

Speed

What is the area beneath the gradient in a velocity-time (v-t) graph used to calculate?

Distance travelled

What is the gradient of a velocity-time/speed-time (v-t or s-t) graph used to calculate?

Acceleration

What is the area beneath a acceleration-time graph used to calculate?

Velocity

What is the one really obscure power equation?

P=fv
(Power = Force applied on the object x Velocity of the object)

What is 1 watt of power?

1 joule per second.

What is work?

Refers to the energy transferred when a force is applied across a distance.

How do you find the density of a solid?

1) Measure the mass of the object using a mass scae
2) To get the volume, measure the volume of water displaced when the object is placed inside a beaker of water.
3) Use the equation, p=m/v, to calculate the density.

What is Hooke’s Law?

Refers to the principle that states that the force applied to an object is directly proportional to the extension of the material.
[F = kΔl]

What is the limit of proportionality?

Refers to the point beyond which Hooke’s Law no longer applies.

What is elastic deformation?

Refers to when the material returns to its original shape with no permanent extension.

What is inelastic deformation?

Refers to when the material is permanently stretched because the atoms have physically moved relative to one another.

What is UTS? (Ultimate tensile strength)

Refers to the maximum stress a material can withstand before breaking.

What is the strength of a material?

Refers to how much force a material can take before it permanently deforms.

What is the toughness of a material?

Refers to how much energy a material can absorb before it breaks.

What are the qualities of a brittle material?

The material fractures without showing any plastic behaviour.

What are the qualities of a ductile material?

The material can be stretched into long wires and remains permanently stretched.

What is Hooke’s Law?

Refers to the principle of the load of a spring and the extension of the spring being directly proportional up until the limit of proportionality.

What is the highest point on a stress-strain curve?

UTS

What happens when Hooke’s Law is obeyed in terms of energy?

Energy stored under the spring = Work done on the spring

What happens when Hooke’s Law is obeyed in terms of equations and energy?

E = 0.5(k)(ΔL)²

What is the gradient of a stress-strain graph?

Young Modulus

What is the area beneath a stress-strain graph?

Stress per unit of volume

How do you calculate the vertical and horizontal components of a force?

1) Vertical => Fsin(θ)
2) Horizontal => Fcos(θ)

What are the 2 states an object can be in when in equilibrium?

1) Travelling at a constant velocity
2) Stationary

What is uniform acceleration?

Refers to when the acceleration of an object is constant

What direction is the force of gravity positive and negative?

1) Downwards => Positive
2) Upwards => Negative

Why isn’t the work being done on an object initially the same as the work done on an object finally?

The object must overcome its initial resistive forces, so more work must be done to move the object.

What is displacement (s)?

Refers to the overall distance travelled from the starting position (which includes a direction due to being a vector quantity)

What is instantaneous velocity?

Refers to the velocity of an object at a specific point in time.

What is average velocity?

Refers to the velocity of an object over a specified time frame.

How do you find the average velocity?

Divide the final displacement by the time taken.

What is free fall?

Refers to when the object experiences an acceleration of g.

How do springs behave when hung in parallel?

1) Extension => Halves
2) Spring constants => Sum spring constants

How do springs behave when hung is series?

1) Extension => Doubles
2) Spring constants => Reciprocal of the spring constants then sum them

What is an ammeter?

Refers to a device that measures the current in the loop of the circuit that is connected in series with.

What is current?

Refers to the rate of flow of charge in a circuit, which is measured in amps.

What is a voltmeter?

Refers to a device used to measure the potential difference across components.

What does the ideal voltmeter have?

Modelled to have infinite resistance.

What is resistance?

Refers to the measure of how difficult it is for current to flow through a material, which is measured in Ohms (Ω)

What is resistivity?

Refers to the quantity that is proportional to an object’s resistance and cross-sectional, and which is inversely proportional to the object’s length, which is measured in Ωm.

What is a superconductor?

Refers to a material which has zero resistivity when the temperature is decreased to the material’s critical temperature.

How do superconductor’s have zero resistivity?

Electrons flow with no energy loss, so current can flow without emf from a battery.

What is terminal potential difference?

Refers to potential difference across the terminals of a power source.

What is Ohm’s Law?

“The current and potential difference are held under constant temperatures are directly proportional.”

How do resistors act in a parallel circuit?

The total resistance is equal to the inverse of the sum of the inverses of the resistances of the resistors.
[Rt = 1/R1 + 1/R2 + ….]

How do resistors act in a series circuit?

The total resistance is equal to the sum of resistances of the resistors.

[Rt = R1 + R2 + …]

What is an ohmic conductor?

Refers to a conductor for which the current flow is directly proportional to the potential difference across it, under constant temperatures.

What is conventional current flow?

Refers to when current flows from the positive (+) to the negative (-) terminal [+ —> -]

What direction is current actually?

Current normally flows from the negative (-) to positive (+) and is the direction that electrons actually flow. [- —> +]

What is current in terms of equations?

I = ΔQ/ΔT

What is 1 ampere?

1 coulomb of charge which passes a point each second

What is potential difference?

Refers to the work done per coulomb of charge travelling in a circuit, which is measured in volts.

What is potential difference in terms of equations?

E = QV so V = E/Q