Physics · Paper 2

Forces

Forces and their interactions, gravity and weight, resultant forces, work done, elasticity, moments, pressure in fluids, atmospheric pressure, motion graphs, Newton's laws, stopping distances and momentum.

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1
Scalars, vectors and forces

Distinguish scalar and vector quantities, describe contact and non-contact forces, and represent forces as vectors.
6 terms
2
Gravity, mass and weight

Use W = mg to calculate weight, and describe how weight and mass are related.
6 terms
3
Resultant forces

Calculate the resultant of forces acting in a straight line, and (Higher tier) use free body diagrams and vector diagrams to find resultants and resolve forces.
6 terms
4
Work done and energy transfer

Use W = Fs to calculate work done, describe the energy transfers, and explain why work done against friction raises temperature.
6 terms
6
Moments, levers and gears

Use M = Fd, the principle of moments for balanced objects, and explain how levers and gears transmit rotational effects.
6 terms
7
Pressure in a fluid

Use p = F ÷ A, explain how pressure in fluids acts at right angles to surfaces, and explain everyday examples of pressure.
6 terms
8
Pressure in a column of liquid and upthrust Higher

Use p = hρg, explain why pressure increases with depth and density, and explain upthrust, floating and sinking (Higher tier).
6 terms
9
Atmospheric pressure

Describe a simple model of the Earth's atmosphere and explain why atmospheric pressure decreases with height.
6 terms
10
Distance, displacement, speed and velocity

Distinguish distance and displacement, speed and velocity, recall typical speeds, and use s = vt.
6 terms
11
Distance–time graphs

Draw and interpret distance–time graphs and use gradients to find speed (and tangents for accelerating objects at Higher tier).
6 terms
12
Acceleration and velocity–time graphs

Use a = Δv ÷ t, interpret velocity–time graphs, and use v² − u² = 2as (and the area under a graph at Higher tier).
6 terms
13
Terminal velocity

Explain terminal velocity in terms of the forces acting on a falling object, and interpret velocity–time graphs for objects reaching terminal velocity.
6 terms
14
Newton's First Law

State and apply Newton's First Law to objects at rest, at constant velocity and with changing motion, and describe inertia (Higher tier).
6 terms
16
Newton's Third Law

State and apply Newton's Third Law to pairs of interacting forces and to equilibrium situations.
6 terms
17
Stopping distance and reaction time

Define stopping distance as thinking distance plus braking distance, describe factors affecting reaction time, and use s = vt for thinking distance.
6 terms
18
Braking distances and large decelerations

Explain the factors that affect braking distance, how brakes work in terms of work done and energy, and the dangers of large decelerations.
6 terms
19
Momentum and its conservation Higher

Use p = mv, and apply conservation of momentum to collisions and explosions (Higher tier).
6 terms
20
Changes in momentum Higher

Use F = mΔv ÷ Δt and explain safety features such as air bags, seat belts, crumple zones and helmets in terms of rate of change of momentum (Higher tier).
6 terms
15
Newton's Second Law

Use F = ma, investigate how force and mass affect acceleration (Required Practical 7), and explain inertial mass (Higher tier).
6 terms
5
Forces and elasticity

Describe elastic and inelastic deformation, use F = ke and E_e = ½ke², and investigate the relationship between force and extension (Required Practical 6).
6 terms

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Key terms in this chapter

All 120, gathered from every lesson.

Scalar: A quantity with magnitude only.
Vector: A quantity with magnitude and direction.
Contact force: A force between objects that are touching.
Non-contact force: A force between objects that are separated.
Magnitude: The size of a quantity.
Newton: The unit of force.
Weight: The force acting on an object due to gravity.
Mass: The amount of matter in an object.
Gravitational field strength: The force per kilogram near a planet.
Newtonmeter: A calibrated spring balance for measuring force.
Centre of mass: The point where the weight of an object may be considered to act.
Directly proportional: Doubling one quantity doubles the other.
Resultant force: A single force with the same effect as all the forces on an object.
Balanced forces: Forces that are equal and opposite.
Free body diagram: A diagram showing all forces acting on an isolated object.
Component: One of two perpendicular forces that together have the same effect as one force.
Resolve: Split a force into two components at right angles.
Equilibrium: When the forces on an object are balanced.
Work done: Energy transferred when a force moves an object.
Joule: The unit of work and energy.
Newton-metre: A joule: one newton moving an object one metre.
Friction: A force between surfaces that opposes motion.
Displacement: The distance moved in a particular direction.
Dissipated: Transferred to less useful stores.
Moment: The turning effect of a force, in newton-metres.
Pivot: The point about which an object turns.
Clockwise: In the direction of a clock's hands.
Anticlockwise: Opposite to the hands of a clock.
Lever: A bar that can turn about a pivot.
Gear: A toothed wheel that transmits rotation.
Pressure: Force per unit area.
Pascal: The unit of pressure; 1 N/m².
Fluid: A liquid or a gas.
Normal: At right angles to a surface.
Area: The size of a surface.
Force: A push or pull.
Upthrust: The resultant upward force on a submerged object due to pressure.
Column of liquid: The liquid above a point.
Density: Mass per unit volume.
Submerged: Completely under the surface.
Displaced: Pushed out of the way.
Average density: Total mass divided by total volume.
Atmosphere: The layer of air around the Earth.
Atmospheric pressure: The pressure caused by air molecules colliding with a surface.
Altitude: Height above the ground or sea level.
Air molecule: A particle of nitrogen, oxygen or another gas.
Less dense: Fewer particles in each cubic metre.
Collision: Particles hitting a surface.
Distance: How far an object moves; a scalar.
Displacement: Distance in a straight line from start to finish with direction; a vector.
Speed: Distance travelled per unit time; a scalar.
Velocity: Speed in a given direction; a vector.
Average speed: Total distance divided by total time.
Uniform motion: Motion at constant speed in a straight line.
Distance–time graph: A graph of distance against time.
Gradient: How steep a line is.
Stationary: Not moving.
Tangent: A straight line that touches a curve at one point.
Constant speed: The same speed all the time.
Accelerating: Speeding up.
Acceleration: The rate of change of velocity.
Deceleration: Slowing down.
Velocity–time graph: A graph of velocity against time.
Uniform acceleration: Constant acceleration.
Free fall: Falling under gravity alone.
Gradient: How steep a line is.
Terminal velocity: The constant velocity reached when the resistive force equals the driving force.
Air resistance: A force opposing motion through air.
Drag: A resistive force in a fluid.
Resultant force: The single force equal to all the forces combined.
Surface area: The size of the surface.
Fluid: A liquid or gas.
Newton's First Law: An object keeps its velocity unless a resultant force acts on it.
Inertia: The tendency of an object to stay at rest or keep moving at constant velocity.
Balanced forces: Forces with a resultant of zero.
Uniform velocity: Constant speed in a straight line.
Resistive force: A force opposing motion.
Driving force: A force that makes a vehicle move.
Newton's Third Law: The forces two interacting objects exert on each other are equal and opposite.
Interaction pair: The two forces in an interaction between two objects.
Equilibrium: When the forces on an object are balanced.
Normal contact force: The push from a surface on an object resting on it.
Reaction force: The force that forms a pair with another force.
Different objects: The two forces in a pair act on separate bodies.
Stopping distance: Thinking distance plus braking distance.
Thinking distance: Distance travelled in the driver's reaction time.
Braking distance: Distance travelled while the brakes slow the vehicle.
Reaction time: The time between a stimulus and a response.
Distraction: Something that takes a driver's attention away.
Mean: The average of repeated readings.
Braking distance: The distance travelled while the brakes slow a vehicle.
Deceleration: A negative acceleration: slowing down.
Friction: A force between surfaces that opposes motion.
Kinetic energy: Energy of a moving object.
Brake fade: Loss of braking power when brakes overheat.
Skid: When tyres lose grip and slide.
Momentum: Mass multiplied by velocity.
Conservation of momentum: Total momentum before an event equals total momentum after in a closed system.
Closed system: A system with no external forces.
Collision: Two objects hitting each other.
Recoil: The backward movement of a gun when fired.
Explosion: When objects push apart from rest.
Rate of change of momentum: Change in momentum divided by time.
Air bag: A cushion that inflates in a collision.
Crumple zone: Part of a vehicle designed to deform in a crash.
Seat belt: A strap that holds a passenger and stretches slightly.
Impact time: The time a collision lasts.
Average force: The mean force over the collision time.
Resultant force: The net force acting on an object.
Acceleration: Rate of change of velocity.
Inertial mass: Force divided by acceleration.
Proportional: Increasing by the same factor.
Inversely proportional: One quantity halves as the other doubles.
Light gate: A sensor that times how long a card takes to pass.
Extension: The increase in length of a spring.
Spring constant: The force needed per metre of extension (N/m).
Limit of proportionality: The point beyond which force and extension are no longer proportional.
Elastic deformation: A change of shape that is reversed when the force is removed.
Inelastic deformation: A permanent change of shape.
Linear: Following a straight line.

Forces

Lessons

Scalars, vectors and forces

Gravity, mass and weight

Resultant forces

Work done and energy transfer

Moments, levers and gears

Pressure in a fluid

Pressure in a column of liquid and upthrust Higher

Atmospheric pressure

Distance, displacement, speed and velocity

Distance–time graphs

Acceleration and velocity–time graphs

Terminal velocity

Newton's First Law

Newton's Third Law

Stopping distance and reaction time

Braking distances and large decelerations

Momentum and its conservation Higher

Changes in momentum Higher

Newton's Second Law

Forces and elasticity

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Key terms in this chapter