Physics F4 2.7 2.8

A tennis ball of mass of 0.05 kg is moving at velocity of 50 m s–1 hits a wall and then bounces back at the same speed. Calculate the impulse produced.

• 0 kg m s–1
• 2.5 kg m s–1
• 5.0 kg m s–1
• 50.0 kg m s–1

A football of mass of 450 g is kicked and its speed before hitting the wall is 20 m s–1. It bounce off the wall at speed of 20 m s–1. The time of collision with the wall is 0.2 s. Calculate the impulsive force acting on the wall.

• 0 N
• 3.6 N
• 90 N
• 90 000N

Which of the following daily life application requires shorter time of collision?

• High jump mats
• Catching high speed ball
• Egg tray'
• Mortar and pestle

‘Follow through’ in playing golf will

• increase the impuls in the collision between the golf club and the golf ball.
• shorten the time of collision between the golf club and the golf ball.
• increase the speed of the golf club after hitting the ball.

A basketball of mass 0.625 kg is thrown horizontally at uniform speed of 10 m s–1 hitting a sponge padded wall. Without rebound, it falls to the floor. If the force acting on the wall is 12.5 N, what is the time of impact?

• 0.5 s
• 0.8 s
• 2.0 s
• 6.3 s

Impulsive force

• is only produced during car collision.
• increases as time of impact decreases.
• increases as change of momentum decrease.
• is not affected by speed of an object.

Newton’s Third Law of Motion state that

• sometimes there is no reaction even if there is an action.
• direction of action is the same as direction of reaction.
• magnitude of action is the same as magnitude of reaction.

Which of the following safety features of a car does not involve in increasing time of impact?

• Front bumper
• Rear easily crumple zone
• Padded dashboard
• Shatterproof windscreen

A car seat belt

• lengthen the time of a car to stop during collision.
• hold the passenger in their seat during head-on collision.
• reduce inertia of the passenger.

Weight of an object

• on Earth and on the moon are the same.
• is constant if its mass is unchanged.
• depends on the gravtitaional field strength of its location.
• is affected by density of an object.