AQA GCSE Physics
AQA GCSE Physics 4.5.6.2.3 Newton's Third Law Exam Questions
Free AQA GCSE Physics exam questions for 4.5.6.2.3 Newton's Third Law, with a mark scheme for every pack. Covers Newton's third law, equal and opposite forces between interacting objects, force pairs and equilibrium situations.
4.5.6.2.3 Newton's Third Law exam questions
2 question packs of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About AQA GCSE Physics 4.5.6.2.3 Newton's Third Law
Newton's third law in AQA GCSE Physics states that whenever two objects interact, the forces they exert on each other are equal and opposite. You need to apply the law to examples of equilibrium situations and identify force pairs correctly. It is examined on Paper 2 and underpins conservation of momentum. Examiners frequently test whether you can tell a third law pair (same type, acting on different objects) from two balanced forces acting on the same object.
What you need to know
- The law Whenever two objects interact, the forces they exert on each other are equal and opposite.
- Features of a force pair The two forces are the same size, act in opposite directions, are the same type of force (for example both gravitational) and act on different objects.
- Examples When you push on a wall, the wall pushes back on you with an equal force. The Earth pulls a falling apple down, and the apple pulls the Earth up with an equal gravitational force.
- Equilibrium situations A book on a table: the book's weight and the normal contact force from the table are balanced but they are not a third law pair, because they act on the same object and are different types.
- Movement A swimmer pushes water backwards and the water pushes the swimmer forwards. A rocket pushes exhaust gases backwards and the gases push the rocket forwards.
Common mistakes in 4.5.6.2.3 Newton's Third Law
- Saying weight and normal contact force on a book are a third law pair. They act on the same object; the pair to the book's weight is the book's gravitational pull on the Earth.
- Thinking the forces in a pair cancel out. They act on different objects, so they cannot cancel.
- Saying the larger object exerts a larger force. Both forces in an interaction pair are always equal in size.
- Missing the type of force when identifying a pair. Both forces must be the same type.
Try three 4.5.6.2.3 Newton's Third Law exam-style questions
1. State Newton's third law. (1 mark)
Show the mark scheme answer
When two objects interact, the forces they exert on each other are equal and opposite.
2. A person stands on the floor. The Earth pulls the person down with a gravitational force of 700 N. Describe the other force in this Newton's third law pair. (3 marks)
Show the mark scheme answer
700 N; gravitational force; exerted by the person on the Earth, acting upwards.
3. Explain how Newton's third law allows a swimmer to move forwards. (2 marks)
Show the mark scheme answer
The swimmer pushes the water backwards; the water exerts an equal and opposite force on the swimmer, pushing them forwards.
4.5.6.2.3 Newton's Third Law FAQs
What does AQA GCSE Physics 4.5.6.2.3 Newton's third law cover?
It covers the law that interacting objects exert equal and opposite forces on each other, and applying it to equilibrium situations.
How do I identify a Newton's third law pair?
Check that the forces are equal in size, opposite in direction, the same type and act on two different objects.
How does the third law link to momentum?
In collisions and explosions, the equal and opposite forces act for the same time, which is why momentum is conserved (4.5.7).
