At a crash test facility scientists run a car of mass m into a wall at a velocity v. The car comes to rest following the collision. The experiment is repeated several times at the same velocity for several different cars (all of mass m).

Given that the mass of the cars and the velocity of the cars are all the same, what aspect of the collision can a car designer try to change to reduce the average force applied to the car (and hence to the occupants of the car)?

A tennis ball of mass 50g is hit against a wall. It hits the wall going right at 5 ms^-1 and rebounds to the left at 4 ms^-1, changing its momentum by 0.45 kg m/s left. The ball is in contact with the wall for 0.2 s and experiences an average force of 2.25 N left (applied by the wall).

What is the force of the ball on the wall?

A tennis ball of mass 50g is hit against a wall. It hits the wall going right at 5 ms^-1 and rebounds to the left at 4 ms^-1, changing its momentum by 0.45 kg m/s left.

If the ball is in contact with the wall for 0.2 s what is the average force applied by the wall on the ball (your answer is a vector)?

A tennis ball of mass 50g is hit against a wall. It hits the wall going right at 5 ms^-1 and rebounds to the left at 4 ms^-1.

What is the change in momentum of the tennis ball?

Question 1 a)

An unlucky driver has become bogged in the mud near a tree. Fortunately,

they find a rope in their car and attach it to the tree and car, and they pull on

the rope as shown in the picture. Also shown is the resulting force diagram,

demonstrating why the technique works: the car experiences a very large force

with a relatively small ‘tug’ applied by the driver.

The

sum of the three forces acting on the centre point of the rope is assumed to be

zero because:

Approximately

what percentage of the ball’s initial kinetic energy (before the bounce) is the

ball’s final kinetic energy (after the bounce)? Give your answer to the nearest

whole number in units of %. Write your answer without units i.e., 12 % as 12.

Question 4 c)

Immediately

Question 4 b)

If

the ball accelerates uniformly when it hits the floor, calculate its

acceleration as it comes to rest before rebounding. Give your answer to the

nearest whole number in units of m/s

Question 4 a)

As

a tennis ball bounces on a hard surface, it undergoes deformation, compressing

and then rebounding. A tennis ball of mass 57.0 g is dropped from a height of

2.4 m onto a concrete surface and rebounds to a height of 1.35 m. During

impact, the ball compresses by approximately 5 mm. Ignore the effects of air

resistance.

How

fast is the ball moving when it hits the concrete surface?

Question 3 c)

The

batters’ muscles must provide the energy taken to swing the bat from rest. If

we model the batter’s swing as having an average speed of 18 m/s over a swing time

period of 200 ms, what is the power output required by the batters’ muscles to

achieve this swing? (Assume 100% of the energy from her muscles is transferred

to the bat.)