 GCSE Science P3 Forces for Transport Revision List | Maths Made Easy

# GCSE Science P3 Forces for Transport Revision List

GCSE Physics P3 (OCR B721): Forces for Transport

Year 11 revision topics for P3 GCSE Science OCR Exam Board

#### P3a Speed

• Use the equation:
• average speed = distance / time
• to include change of units from km to m.
• Understand why one type of speed camera takes two photographs:
• a certain time apart
• when the vehicle moves over marked lines a known distance apart on the road
• Draw and interpret qualitatively graphs of distance against time.
• Looking at data from cars, sport and animals then transferring it to graphical form for analysis (distance- time graphs).
• Understand how average speed cameras work.
• Interpret the relationship between speed, distance and time including:
• increasing the speed, which increases the distance travelled in the same time
• increasing the speed reduces the time needed to cover the same distance.
• Use the equation, including a change of subject:
• distance = average speed × time = (u + v) × t / 2
• Interpret the relationship between speed, distance and time to include the effect of changing any one or both of the quantities.(HL)
• Use the equation, including a change of subject and/ or units:(HL)
• distance = average speed × time = (u + v) × t / 2
• Describe and interpret the gradient (steepness) of a distance-time graph as speed (higher speed gives steeper gradient).
• Draw and interpret graphs of distance against time:(HL)
• qualitatively for non-uniform speed
• calculations of speed from the gradient of distance-time graph for uniform speed.

#### P3b Changing Speed

• Describe the trends in speed and time from a simple speed-time graph:
• a) horizontal line – constant speed
• b) straight line positive gradient – increasing speed
• c) straight line negative gradient – decreasing speed.
• Recognise that acceleration involves a change in speed (limited to motion in a straight line):
• a) speeding up involves an acceleration
• b) slowing down involves a deceleration
• c) greater change in speed (in a given time) results in higher acceleration.
• Know that acceleration is measured in metres per second squared (m/s2).
• Use the equation: acceleration = change in speed / time taken
• when given the change in speed.
• Understand that the velocity of an object is its speed combined with its direction.
• Recognise that direction is important when describing the motion of an object.
• Describe, draw and interpret qualitatively, graphs of speed against time for uniform acceleration to include:
• greater acceleration shown by a higher gradient
• the significance of a positive or negative gradient
• calculations of distance travelled from a simple speed-time graph for uniform acceleration.
• Describe, draw and interpret graphs of speed against time including:(HL)
• quantitatively for uniform acceleration
• calculations of distance travelled from a speed- time graph for uniform acceleration
• calculations of acceleration from a speed-time graph for uniform acceleration
• qualitative interpretation of speed-time graphs for non-uniform acceleration.
• Describe acceleration as change in speed per unit time and that:
• increase in speed results from a positive acceleration
• decrease in speed results from a negative acceleration or deceleration.
• Use the equation including prior calculation of the change in speed:
• acceleration = change in speed / time taken
• Explain how acceleration can involve either a change:(HL)
• in speed
• direction
• in both speed and direction.
• Interpret the relationship between acceleration, change of speed and time to include the effect of changing any one or two of the quantities.(HL)
• Use the equation, including a change of subject:
• acceleration = change in speed / time taken
•
• Recognise that for two objects moving in opposite directions at the same speed, their velocities will have identical magnitude but opposite signs.
• Calculate the relative velocity of objects moving in parallel.

#### P3c: Forces and Motion

• Recognise situations where forces cause things to:
• speed up
• slow down
• stay at the same speed.
• Use the equation:
• force = mass × acceleration
• F = ma
when given mass and acceleration.
• Describe thinking distance as the distance travelled between the need for braking occurring and the brakes starting to act.
• Describe braking distance as the distance taken to stop once the brakes have been applied.
• Describe stopping distance as thinking distance + braking distance.
• Calculate stopping distance given values for thinking distance and braking distance.
• Explain why thinking, braking and stopping distances are significant for road safety.
• Describe and interpret the relationship between force, mass and acceleration in everyday examples.
• Use the equation, including a change of subject:
• force = mass × acceleration
• Use the equation, including a change of subject and the need to previously calculate the accelerating force:(HL)
• force = mass × acceleration
• Explain how certain factors may increase thinking distance:
• driver tiredness
• influence of alcohol or other drugs
• greater speed
• distractions or lack of concentration.
• Explain how certain factors may increase braking distance:
• car conditions
• greater speed.
• Interpret data about thinking distances and braking distances.
• Explain the implications of stopping distances in road safety:
• driving too close to the car in front (ie inside thinking distance)
the police call it ‘tail-gating’
• speed limits
• Explain qualitatively everyday situations where braking distance is changed including:(HL)
• friction
• mass
• speed
• braking force.
• Draw and interpret the shapes of graphs for thinking and braking distance against speed.(HL)
• Explain the effects of increased speed on:(HL)
• thinking distance – increases linearly
• braking distance – increases as a squared relationship eg if speed doubles braking distance increases by a factor of four, if speed trebles braking distance increases by a factor of nine.

#### P3d Work and Power

• Know everyday examples in which work is done and power is developed to include:
• lifting weights
• climbing stairs
• pulling a sledge
• pushing a shopping trolley.
• Describe how energy is transferred when work is done.
1. Understand that the amount of work done depends on:
2. the size of the force in newtons (N)
3. the distance travelled in metres (m).
• Know that the joule (J) is the unit for both work and energy.
• Use the equation:
• work done = force × distance
• Know that power is measured in watts (W).
• The plenary could focus on how efficient the human body is as a machine.
• Describe power as a measurement of how quickly work is being done.
• Recognise that cars:
• have different power ratings
• have different engine sizes
• and these relate to different fuel consumptions.
• Use the equation:
• weight = mass × gravitational field strength
• Use the equation, including a change of subject:(HL)
• weight = mass × gravitational field strength
• Use the equation, including a change of subject:
• work done = force × distance
• Use the equation:(HL)
• work done = force × distance
and then use the value for work done in the power equation below.
• Use the equation:
• power = work done / time
• Interpret fuel consumption figures from data on cars to include:
• environmental issues
• costs.
• Use the equation, including a change of subject:(HL)
• power = work done / time
when work has been calculated.
• Use and understand the derivation of the power equation in the form:(HL)
• power = force × speed

#### P3e: Energy on the Move

• Understand that kinetic energy (KE) depends on the mass and speed of an object.
• Recognise and describe (derivatives of) fossil fuels as the main fuels in road transport eg petrol and diesel.
• Know that bio-fuels and solar energy are possible alternatives to fossil fuels.
• Describe how electricity can be used for road transport, and how its use could affect different groups of people and the environment:
• battery driven cars
• solar power / cars with solar panels.
• Draw conclusions from basic data about fuel consumption, including emissions (no recall required).
• Recognise that the shape of a moving object can influence its top speed and fuel consumption:
• wedge shape of sports car
• deflectors on lorries and caravans
• roof boxes on cars
• driving with car windows open.
• Use and apply the equation:
• KE = 1/2 mv2
• Use and apply the equation:(HL)
• KE = 1/2 mv2
• including a change of subject ie
v = √ (2KE/m) and m = 2/KE/(v2)
• Apply the ideas of kinetic energy to:(HL)
• relationship between braking distances and speed
• everyday situations involving objects moving.
• Describe arguments for and against the use of battery powered cars.
• Explain why electrically powered cars do not pollute at the point of use whereas fossil fuel cars do.
• Recognise that battery driven cars need to have the battery recharged:
• this uses electricity produced from a power station
• power stations cause pollution.
• Explain why we may have to rely on bio-fuelled and solar powered vehicles in the future.
• Explain how bio-fuelled and solar powered vehicles:(HL)
• reduce pollution at the point of use
• produce pollution in their production
• may lead to an overall reduction in CO2 emissions.
• Interpret data about fuel consumption, including emissions.
• Explain how car fuel consumption figures depend on:(HL)
• energy required to increase KE
• energy required to do work against friction
• driving styles and speeds
• Evaluate and compare data about fuel consumption and emissions.(HL)

#### P2f: Crumple Zones

• Use the equation:
• momentum = mass × velocity
to calculate momentum.
• Know that a sudden change in momentum in a collision, results in a large force that can cause injury.
• Describe the typical safety features of modern cars that require energy to be absorbed when vehicles stop:
• eg heating in brakes, crumple zones, seat-belts, airbags.
• Explain why seatbelts have to be replaced after a crash.
• Recognise the risks and benefits arising from the use of seatbelts.
• Know and distinguish between typical safety features of cars which:
• are intended to prevent accidents, or
• are intended to protect occupants in the event of an accident.
• Use the equation including a change of subject:
• momentum = mass × velocity
• Describe why the greater the mass of an object and/ or the greater the velocity, the more momentum the object has in the direction of motion.
• Use the equation:
• force = change in momentum / time
to calculate force
• Use and apply the equation including a change of subject:
• force = change in momentum / time
• Use Newton’s second law of motion to explain the above points:(HL)
• F = ma
• Explain how spreading the change in momentum over a longer time reduces the likelihood of injury.
• Explain, using the ideas about momentum, the use of crumple zones, seatbelts and airbags in cars.
• Explain why forces can be reduced when stopping (eg crumple zones, braking distances, escape lanes, crash barriers, seatbelts and airbags) by:(HL)
• increasing stopping or collision time
• increasing stopping or collision distance
• decreasing acceleration.
• Describe how test data may be gathered and used to identify and develop safety features for cars.
• Evaluate the effectiveness of given safety features in terms of saving lives and reducing injuries.(HL)
• Describe how seatbelts, crumple zones and airbagsare useful in a crash because they:
• change shape
• absorb energy
• reduce injuries
• Analyse personal and social choices in terms of risk and benefits of wearing seatbelts.(HL)
• Describe how ABS brakes:(HL)
• make it possible to keep control of the steering of a vehicle in hazardous situations (eg when braking hard or going into a skid)
• work by the brakes automatically pumping on and off to avoid skidding
• sometimes reduce braking distances.

#### P3g: Falling safely

• Recognise that frictional forces (drag, friction, air resistance):
• act against the movement
• lead to energy loss and inefficiency
• can be reduced (shape, lubricant).
• Explain how objects falling through the Earth’s atmosphere reach a terminal speed.
• Understand why falling objects do not experience drag when there is no atmosphere.
• Explain in terms of the balance of forces how moving objects:
• increase speed
• decrease speed
• Explain, in terms of balance of forces, why objects reach a terminal speed:(HL)
• higher speed = more drag
• larger area = more drag
• weight (falling object) or driving force (eg a car) = drag when travelling at terminal speed.
• Recognise that acceleration due to gravity (g) is the same for any object at a given point on the Earth’s surface.
• Understand that gravitational field strength or acceleration due to gravity:(HL)
• is unaffected by atmospheric changes
• varies slightly at different points on the Earth’s surface
• will be slightly different on the top of a mountain or down a mineshaft.

#### P2h Energy of games and Theme rides

• Describe everyday examples in which objects have gravitational potential energy (GPE).
• Recognise everyday examples in which objects use gravitational potential energy (GPE).
• Recognise that objects have gravitational potential energy (GPE) because of their mass and position in Earth’s gravitational field.
• Use the equation:
• GPE = mgh
• Recognise and interpret examples of energy transfer between gravitational potential energy (GPE) and kinetic energy (KE).
• Understand that for a body falling through the atmosphere at terminal speed:(HL)
• kinetic energy (KE) does not increase
• gravitational potential energy (GPE) is transferred to increased internal or thermal energy of the surrounding air particles through the mechanism of friction.
• Use and apply the equation, including a change of subject:(HL)
• GPE = mgh
• Interpret a gravity ride (roller-coaster) in terms of:
• a) kinetic energy (KE)
• b) gravitational potential energy (GPE)
• c) energy transfer.
• Describe the effect of changing mass and speed on kinetic energy (KE):
• a) doubling mass doubles KE
• b) doubling speed quadruples KE.
• Use and apply the relationship(HL)
• mgh = 1/2 mv2
• Show that for a given object falling to Earth, this relationship can be expressed as(HL)
• h = v2 ÷ 2g
and give an example of how this formula
h = v2/2g could be used.