12.6 CHAPTER 12. FORCE,MOMENTUM AND IMPULSE
0,1 0,2 0,3 0,4 0,5
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100
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Time (s)
Force (N)
(a) What does the areaunder this graph represent?
(b) Calculate the speedat which the ball leavesthe hockey stick.
(c) The same player hits a practise ball of the same mass, but which ismade from
a softer material. The hit is such that the ball moves off with the same speed as
before. How will the area, the height and the base of the triangle that forms the
graph, compare with that of the original ball?
- The fronts of modern cars are deliberatelydesigned in such a waythat in case of a
head-on collision, the front would crumple. Why is it desirable that thefront of the
car should crumple?
- A ball of mass 100g strikes a wall horizontally at 10 m·s−^1 and rebounds at 8 m·s−^1.
It is in contact with thewall for 0,01 s.
(a) Calculate the average force exerted by the wall on the ball.
(b) Consider a lump of putty also of mass 100 g which strikes the wall at 10m·s−^1 and
comes to rest in 0,01 sagainst the surface. Explain qualitatively (no numbers)
whether the force exerted on the putty will be less than, greater than of the same
as the force exerted on the ball by the wall. Donot do any calculations.
- Shaun swings his cricket bat and hits a stationary cricket ball vertically upwards so
that it rises to a height of 11,25 m above the ground. The ball has a mass of 125 g.
Determine
(a) the speed with which the ball left the bat.
(b) the impulse exertedby the bat on the ball.
(c) the impulse exertedby the ball on the bat.
(d) for how long the ball is in the air.
- A glass plate is mounted horizontally 1,05m above the ground. An iron ball of
mass 0,4 kg is releasedfrom rest and falls a distance of 1,25 m beforestriking the
glass plate and breakingit. The total time takenfrom release to hitting the ground is
recorded as 0,80 s. Assume that the time taken to break the plate is negligible.
1,25 m
1,05 m
