Identify the effect of force in each of the following:
(a) compressing a spring
(b) a tennis player hitting a ball
(c) stopping a moving car
(d) kicking a stationary football.
Answers
1)When a spring is stretched or compressed, so that its length changes by an amount x from its equilibrium length, then it exerts a force F = -kx in a direction towards its equilibrium position. The force a spring exerts is a restoring force, it acts to restore the spring to its equilibrium length.
2)Consider a tennis player hitting a ball, (a) Identify the action-reaction pairs when the ball is being hit and (b) while the ball is in flight. (a) As a tennis player hits ball with her racquet, the racquet exerts forward force on the ball. This is action force.
3) Inertia wants to keep an object moving at the same rate. when you stop a car. the matter in the car wants to keep doing what its doing for example, you’re going 45MPH and you brake. you and the car wants to keep going so you feel the force pushing you backwards. when the car finally stops. you will feel a jolt pressing you into your seat which is caused by the force pushing you backwards suddenly stops. so it returns to normal and you feel the force. Pro Tip : to stop the jolt you press the brake and before you stop slowly reduce the pressure on the brake pedal and make the car stop smoothly.