AQA GCSE Physics (8463), Higher tier · Forces › Forces and motion › Newton's laws of motion
Practise Newton's Third Law. 11 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
State Newton’s Third Law.
When two objects interact, the forces they exert on each other are equal and opposite.
Give the size and direction of the force that the rope exerts on team A. Name the law that explains this.
1800 N towards team B (Newton’s Third Law).
Give the size and direction of the force that the exhaust gases exert on the engines.
45 kN forwards.
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
(a) State Newton’s Third Law.[2]
(b) A swimmer pushes backwards on the water with a force of 150 N. Give the size and direction of the force that the water exerts on the swimmer.[2]
Show the answer and mark scheme
(a)Answer: When two objects interact, the forces they exert on each other are equal and opposite.
when two objects interact, they exert forces on each other
that are equal (in size) and opposite (in direction)
(b)Answer: 150 N forwards.
150 (N)
forwards
Question 2Medium5 marks
A book rests on a table. The weight of the book is 8.0 N.
(a) The weight of the book is the gravitational force of the Earth on the book. Describe the force that forms a Newton’s Third Law pair with the weight of the book.[3]
(b) The table exerts a normal contact force of 8.0 N upwards on the book. A student says: ‘The weight of the book and the normal contact force are a Newton’s Third Law pair.’ Explain why the student is wrong.[2]
Show the answer and mark scheme
(a)Answer: The gravitational force of the book on the Earth: 8.0 N, upwards.
the gravitational force of the book on the Earth
8.0 N
upwards (towards the book)
(b)Answer: Both forces act on the book (a third-law pair acts on two different objects), and they are different types of force.
both forces act on the same object (the book), but the forces in a Newton’s Third Law pair act on different objects
they are different types of force (gravitational and contact) / the partner of the normal contact force is the downward push of the book on the table
Question 3Hard7 marks
Two teams, A and B, take part in a tug of war. At first the rope is stationary. Team A pulls on the rope with a force of 1800 N.
(a) What force does team B exert on the rope? Give a reason for your answer.[2]
(b) Give the size and direction of the force that the rope exerts on team A. Name the law that explains this.[2]
(c) Team A starts to pull team B towards them. A student says: ‘Team A must now be pulling on the rope harder than the rope pulls on team A.’ Explain why the student is wrong and what makes team A win.[3]
Show the answer and mark scheme
(a)Answer: 1800 N, because the rope is in equilibrium.
1800 N (in the opposite direction)
the rope is stationary / in equilibrium, so the resultant force on it is zero
(b)Answer: 1800 N towards team B (Newton’s Third Law).
1800 N towards team B
Newton’s Third Law
(c)Answer: The rope and team A always exert equal and opposite forces; team A wins because the ground pushes team A with a larger friction force, while team B’s friction is less than the rope’s pull.
the force of team A on the rope is always equal to the force of the rope on team A (Newton’s Third Law)
team A pushes harder (backwards) on the ground, so the ground exerts a larger (friction) force on team A
the friction force on team B is less than the pull of the rope on team B, so there is a resultant force on team B towards team A