According to Newton’s third law, for every force there is always a reaction force of equal magnitude and opposite direction. In each of the examples below, identify an action–reaction pair of forces.
(a) A tennis racket hits a tennis ball, exerting a force on the ball.
(b) Two ice skaters are initially at rest and in contact. One of the skaters then pushes on the other skater’s back, exerting a force on that skater.
(c) A car is moving at high speed and runs into a tree, exerting a force on the tree.
(d) Two cars are moving in opposite directions and collide head-on.
(e) A person leans on a wall, exerting a force on the wall.
(f) A hammer hits a nail, exerting a force on the nail.
(g) A mass hangs by a string tied to a ceiling, with the string exerting a force on the mass.
(h) A bird sits on a telephone pole, exerting a force on the pole.