PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
Four students were discussing Newton’s Third Law. They wrote the following statements on the board:
S1: "The action force always appears first, and only after some time the reaction force starts acting."
S2: "Action and reaction act on the same body and therefore cancel each other completely."
S3: "If two bodies exert equal and opposite forces on each other, both bodies must remain at rest."
S4: "While walking, the ground pushes the foot forward with a force equal in magnitude to the backward force exerted by the foot on the ground."
Analyse these statements and answer the questions below.
(a) Identify which of the above statements are incorrect.
(b) Rewrite each incorrect statement in a scientifically accurate form.
(c) Choose any one of the corrected statements and illustrate it with a suitable everyday example, clearly naming the two bodies involved and the pair of forces acting between them.