1. (a) If a rubber ball or marble is placed on a very smooth surface and given a small push, it starts moving with some speed.
(b) If a child is placed on a hanging swing in the state of rest and the swing is pulled again and again by a rope, the swing will move to and fro with a speed.
2. (i) If an inflated balloon is taken and pressed from two sides with hand, its shape get changed.
(ii) If a plate of steel is beaten up with a hammer the shape of the plate will get change.
3. Fill in the blanks
(a) To draw water from a well we have to pull at the rope.
(b) A charged body attracts an uncharged body towards it.
(c) To move a loaded trolley we have to pull
(d) The north pole of a magnet repels the north pole of another magnet.
4. (a) shape
(d) gravity, friction.
6. The shape of the hot piece of iron changes. It flattens and becomes thinner than earlier. This is the effect of force due to hammering the piece of iron.
7. This is an electrostatic force.
8. The forces that act on the bucket are as follows:-
(i) The pressure of water contained in it, exerted on its wall and on base of the
(ii) Force of gravity by earth.
(iii) The water is contained in a bucket and the pressure of force is exerted on the wall of the bucket, which is sufficient to take it as a force.
As the bucket is held in my hand, so I overcome the force of gravity of the earth. That is why these forces do not bring a change in the state of motion.
9. The two forces that are acting on the rocket immediately after leaving the launching pad are:
(a) Force of gravity of earth acting downward and
(b) The frictional force produced by air particles.
10. (d) Atmospheric pressure.