Question

1. A 5 kg mass is initially traveling forwards at 10 m/s. It collides with a wall and rebounds with a speed of 5 m/s. What is the magnitude of the object's change in momentum?

a) 5 kg m/s

b) 25 kg m/s

c) 50 kg m/s

d) 75 kg m/s

2. Compare punching a wall to punching a bed. It takes more time for your hand to come to rest when punching a bed than when punching a wall. As a result,

a) the impulse the bed exerts on your hand is larger than the impulse the wall exerts on your hand

b) the impulse the bed exerts on your hand is smaller than the impulse the wall exerts on your hand

c) the average force exerted by the bed is larger than the average force exerted by the wall

d) the average force exerted by the bed is smaller than the average force exerted by the wall

3. A 2 kg mass is traveling in the forward direction with a speed of 3 m/s. It receives an impulse in the forward direction of 4 kg m/s over a time period of 5 seconds. What is the object's speed after those 5 seconds?

a) 5 m/s

b) 7 m/s

c) 10 m/s

d) 26 m/s

4. A clay ball and a rubber ball of equal masses are falling towards the ground with the same initial velocity. The clay ball sticks to the ground and the rubber ball bounces upwards after hitting the ground. Which of the following is true?

a) the ground exerts a larger impulse on the clay ball than it does on the rubber ball

b) the ground exerts a larger impulse on the rubber ball than it does on the clay ball

c) the ground exerts the same impulse on the clay ball as it does on the rubber ball

d) it depends on the speed of the balls

5. John (mass 50 kg) is standing in a boat (mass 70 kg) and holding an anchor (30 kg). He throws the anchor horizontally forwards with a speed of 2 m/s. What will happen to John and the boat?

a) they will remain stationary

b) they will travel backwards with an initial speed of 2 m/s

c) they will travel backwards with an initial speed of 0.5 m/s

d) they will travel backwards with an initial speed of 4 m/s

Answer 1

1.) We know that the change in momentum

Here V=-5 m/s ( - due to opposite direction ) ., U=10 m/s

in magnitude

2) We know that the force

since is same in both case but is larger for bed than wall So Answer is

the average force exerted by the bed is smaller than the average force exerted by the wall.

3) We know that the Impulse   

F=4.0/5=0.80 N

As you know F=Ma so a=F/M =0.80/2.0 =0.40 m/s/s

Using equation of the motion

v=u+at

v=3.0+0.4*5=5.0 m/s

v=5.0 m/s answer