Forces | OCR GCSE Combined Science Physics, Foundation tier (J250)
Forces
- 255 questions
- 15 subtopics
- Paper 5 (Physics)
- Paper 5 (Physics)
Forces is examined in Paper 5 (Physics).
It covers measuring distance and time, and calculating speed, converting units, and rates, vectors and scalars in motion, distance-time and velocity-time graphs, average speed, and the equations of uniform motion, how objects interact, and forces as vectors, newton's first law, newton's second law, work done, and stored energy, power, and Newton's third law, stretching, bending and compressing; elastic and plastic, force and extension, linear and non-linear, the spring constant, and work done in stretching, gravitational fields, weight and free fall and calculations with weight and gravitational field strength.
Sample questions from Forces
Answer each one closed book first, then open the answer.
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Measuring distance and time, and calculating speed
A cyclist travels 450 m in 30 s. What is her average speed?
Show the answer
450 ÷ 30 = 15 m/s. -
Converting units, and rates
Give the powers of ten for the prefixes deci, centi, milli, micro and nano.
Show the answer
Deci is 10⁻¹, centi is 10⁻², milli is 10⁻³, micro is 10⁻⁶ and nano is 10⁻⁹. -
Distance-time and velocity-time graphs
A distance–time graph curves upwards, getting steeper and steeper. What is happening to the motion?
Show the answer
The object is speeding up, because the gradient and therefore the speed is increasing. -
Average speed, and the equations of uniform motion
Describe how two light gates can be used to measure the acceleration of a trolley running down a ramp.
Show the answer
Fix a card of known length to the trolley; each gate times how long the card takes to pass, giving a speed at each gate of card length ÷ time, and the time to travel between the gates is recorded, so acceleration = change in speed ÷ that time. -
Newton's first law
What three changes to an object's motion can a resultant force produce?
Show the answer
It can make the object speed up, slow down, or change direction. -
Newton's second law
A ball of mass 0.5 kg is struck with a resultant force of 200 N. What is its acceleration?
Show the answer
200 ÷ 0.5 = 400 m/s². -
Power, and Newton's third law
A student does 1500 J of work running up a flight of stairs in 6 s. What is her useful power output?
Show the answer
1500 ÷ 6 = 250 W. -
Stretching, bending and compressing; elastic and plastic
A spring is stretched by a load and returns exactly to its original length when the load is taken off. Which type of deformation has taken place?
Show the answer
Elastic deformation.
The 15 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Measuring distance and time, and calculating speed | Instruments for measuring length and time, why light gates beat a hand-held stopwatch, how reaction time is reduced, and finding speed from distance, time and the gradient of a distance-time graph. | 28 |
| Converting units, and rates | The standard units of distance and time, converting kilometres per hour to metres per second, minutes to seconds and centimetres to metres, and why units must match in an equation. | 21 |
| Vectors and scalars in motion | The difference between a scalar and a vector, why distance is a scalar and displacement a vector, how velocity differs from speed, and journeys where the two disagree. | 10 |
| Distance-time and velocity-time graphs | What horizontal, steeper and curving lines mean on a distance-time graph, what the gradient and horizontal or downward-sloping lines show on a velocity-time graph, calculating acceleration from the gradient, and describing a journey from its graph. | 8 |
| Average speed, and the equations of uniform motion | How average speed is found for a changing journey, distance, speed and time calculations, acceleration from a change in velocity, and the equation linking final velocity, starting velocity, acceleration and distance. | 23 |
| How objects interact, and forces as vectors | The four ways objects interact and which act at a distance, normal contact force and friction, the equal and opposite pair of forces produced by every interaction, free body force diagrams, and finding the resultant of forces acting along one line. | 21 |
| Newton's first law | What happens to an object with no resultant force on it, what a resultant force can change, and why spacecraft, books, cyclists and sliding loads behave as they do. | 10 |
| Newton's second law | The relationship between resultant force, mass and acceleration, what one newton means, calculations of force, mass and acceleration for trolleys, cars and balls, and why a loaded lorry accelerates more slowly than an empty one under the same driving force. | 9 |
| Work done, and stored energy | How work done is calculated and its unit, why holding a bag still does no work, where energy goes when work is done against friction, and the energy in a moving object's kinetic store. | 16 |
| Power, and Newton's third law | The definition and unit of power with calculations for motors, lamps and stairs, the law describing interaction pairs, and why the two forces of a pair never cancel each other. | 16 |
| Stretching, bending and compressing; elastic and plastic | The three ways forces change shape and why at least two forces are needed, the forces that stretch a spring, bend a diving board and compress a pillar, elastic and plastic deformation and how to tell them apart, and why an overstretched spring stays longer. | 16 |
| Force and extension, linear and non-linear | Extension and how to calculate it, direct proportion up to the limit of proportionality, the elastic limit, linear and non-linear force-extension graphs, and the spring-stretching investigation with its variables, precautions, results table, hypothesis, length against force graph and conclusion. | 29 |
| The spring constant, and work done in stretching | What the spring constant measures and its unit, force = spring constant × extension with calculations and stiffness comparisons, work done in stretching as stored energy, work done = ½ × spring constant × extension², the area under a force-extension graph, and the effect of doubling the extension. | 17 |
| Gravitational fields, weight and free fall | Gravitational fields around every mass and why they only attract, field strength on the Earth and the Moon, weight as a force measured in newtons with a newtonmeter, how mass differs from weight, the centre of mass, and free fall at about 10 m/s² whatever the mass. | 21 |
| Calculations with weight and gravitational field strength | The relationship between weight, mass and gravitational field strength, its rearrangements, worked examples on the Earth and a moon, and how weight and mass behave when the field strength changes. | 10 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby topics
OCR GCSE Combined Science Physics, Foundation tier Active Recall Guide
Every topic, not just this one. 1,084 questions with their answers.