A person standing on a riverbank pulls a small boat towards the shore by means of a light
PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A person standing on a riverbank pulls a small boat towards the shore by means of a light, horizontal rope. The rope passes over a fixed, frictionless pulley on the bank, so that the person pulls downward on the free end of the rope while the other end is tied to the bow of the boat.
Answer the following questions related to the forces in this situation.
(i) List four distinct action–reaction pairs that occur among the person, the rope, the boat and the Earth.
(ii) Draw separate free-body diagrams for (a) the person, (b) the rope segment in the person’s hand, and (c) the boat. Label each force and indicate which ones belong to the action–reaction pairs named in part (i).
(iii) Explain why the boat moves towards the shore even though the horizontal forces acting on the boat and the person are equal and opposite.