1.    Meteor Crater in Arizona is thought to have been formed by the impact of a meteor with the Earth some 20,000 years ago. The mass of the meteor is estimated at 5 x 10¹⁰ kg, and its speed at 7200 ms^-1.
   What speed would such a meteor impart to the Earth in a head-on collision?.

2.  (i)How is the recoil of a gun an example of the law of conservation of momentum?
    How is a rocket being launch an example of Newton's third law?

   (ii)A 10 kg gun recoils with a speed of 0.1 ms^-1 as it fires a 0.001 kg bullet. Neglecting friction, what is the speed of the bullet as it leaves the gun?

3.    A 1 kg ball hits a surface perpendicularly with a speed of 3 ms^-1 and bounces back with a speed of 2 ms^-1. How much change in momentum does the ball undergo?

4.    A body K of mass 0.20 kg and moving at a speed of 6.0 ms^-1 collides with a stationary body L of mass 1.0 kg. K then rebounds from the collision with a speed of 4.0 ms^-1 and L is driven fowards with a speed of 2.0 ms^-1. Given that the collision is elastic, calculate the impulse applied to L by K.

5.    A steel ball of mass 0.500 kg is fastened to a cord 70.0 cm long and fixed at the far end, and is released when the cord is horizontal. At the bottom of its path, the all strikes a 2.5 kg steel block initially at rest on a frictionless surface. The collision is elastic.
Find
   (a) the speed of the ball and
   (b) the speed of the block,
both just after the collision.

6.    Two titanium spheres approach each other head-on with the same speed and collide elastically. After the collision, one of the spheres, whose mass is 300 g, remains at rest.
(a) What is the mass of the other sphere?
(b) What is the speed of the two-sphere center of mass if the initial speed of each sphere was 2.0 ms^-1?

7.    A barge with mass 1.5 x 10⁵ kg is proceeding down river at 6.2 ms^-1 in heavy fog when it collides broadside with a barge heading directly across the river. The second barge has mass 2.78 x 10⁵ kg and was moving at 4.3 ms^-1. Immediately after impact, the second barge finds its course deflected by 18⁰ in the downriver direction and its speed increased to 5.1 ms^-1. The river current was practically zero at the time of the accident. (a) What are the speed and direction of motion of the first barge immediately after the collision? (b) How much kinetic energy is lost in the collision?

8.    Hard ground can bring an object from high speed to rest in a very short period of time, while a soft object needs a long time. Why is this so? and is it true that when an object hits the ground, the action force is exerted by the ground on the object, while the force exerted by the object is the reaction force? When you are falling in the air in the case of free fall, is it true that you experience no force exerted upwards on you? Then where is the air resistance? When you are falling with parachute and are falling in terminal velocity, if you exert a force on the air, will you float upwards in the air? Will there be any parachute whose surface area is so large that when you open it when falling, you won't fall but will float upwards in the air? If body A exerts a force on body B, but the force is the maximum force body B can take, what will happen to B? In this case will B still exert an equal amount of force on A? Why some of the insects can float on water? Is it because they are too light and water can exert a force equals its weight, i.e, their weight is less than the maximum force water can exert at the surface, so they can float.

9.    Why does a hard object need a short time while a soft object need a long time to bring an object from high speed to rest. Although the momentum change is the same, I want to know why one needs more time and one less time. Which is the action force when the onject hit the ground, the force exerted by the object or by the ground? If I kick into the air while falling with parachute, won't I float upwards? not even for a short moment? 10.    The force exerted is much greater force on hard ground than on soft ground. The object is the same, why is the force exerted is different? For example, if it takes 5 seconds to stop an object landing from 180ms^-1 to rest, the object exert a constant force of 36 N on the ground while the ground exert a constant force of 36 N back on the object which bring it to rest after five minutes? Why can't we stand without putting our feet on the ground? Why are there so many stones on the railway tracks? Why we cannot fill a water bottle to the very full if the water is from a water-cooler and the water is coming down at high speed?

11.    i) I still don't get it. The object is the same, and since the force exerted by the ground is the reaction force, then the force exerted by the object on the ground should be the same (the object is the same). Why is it different for hard and soft ground? Is it true that when falling onto soft ground, there is other force which cause the net force exerted by the object on the soft ground to be less than that on hard ground?
ii) If the whole world including man,animals, fishes jump on the ground at the same time, will the force be so great that the earth will have a noticeably acceleration and will overcome the solar gravitation force and leave the solar system?

12.     What I mean is, the object is the same, but why in one case one exert 36 N on the ground, but in the other case it exert 0.6 N on the ground? Shouldn't the force be the same provided that the mass and the acceleration of the body is the same?

13.     What is the real reason behind the difference in the magnitude of the forces, for a object of same mass and same weight?

14.     With the World Cup kicking off shortly, can you give me some information on the physics of football?

In any collision between two objects, what is true about the total momentum and the total kinetic energy of the system of two objects?

	Total momentum	Total kinetic energy
A	always stays the same	always stays the same
B	always stays the same	can change
C	can change	always stays the same
D	can change	can change

Distinguish between an elastic and an inelastic collision. (2 marks)
Explain the relevance to elastic collisions of the principles of
(i) conservation of linear momentum,
(ii) conservation of energy (4 marks)

By applying these principles in algebraic form, show that, for an elastic collision of two particles involving no angular deflection,
relative velocity of approach = - relative velocity of separation ( 5 marks)