FORCE AND PRESSURE

It is much easier to burst an inflated balloon with a needle than
by a finger. Explain.

Two women are of the same weight. One wears sandals with
pointed heels while the other wears sandals with flat soles. Which
one would feel more comfortable while walking on a sandy beach?
Give reasons for your answer.

It is difficult to cut cloth using a pair of scissors with blunt blades.
Explain.

An archer shoots an arrow in the air horizontally. However, after
moving some distance, the arrow falls to the ground. Name the
initial force that sets the arrow in motion. Explain why the arrow
ultimately falls down.

Fruits detached from a tree fall down due to force of gravity. We
know that a force arises due to interaction between two objects.
Name the objects interacting in this case.

Two thermocol balls held close to each other move away from
each other. When they are released, name the force which might
be responsible for this phenomenon. Explain.

Two persons are applying forces on two opposite sides of a moving
cart. The cart still moves with the same speed in the same
direction. What do you infer about the magnitudes and direction
of the forces applied.

Does the force of gravitation exist between two astronauts in
space?

A gas filled balloon moves up. Is the upward force acting on it
larger or smaller than the force of gravity?

Does force of gravity act on dust particles?

While sieving grains, small pieces fall down. Which force pulls
them down?

During dry weather, clothes made of synthetic fibre often stick to
the skin. Which type of force is responsible for this phenomenon?

A girl is pushing a box towards east direction. In which direction
should her friend push the box so that it moves faster in the
same direction?

Where do we apply a force while walking?

A ball of dough is rolled into a flat chapatti. Name the force
exerted to change the shape of the dough.

When we press the bulb of a dropper with its nozzle kept in water, air in the dropper is seen to escape in the form of bubbles. Once we release the pressure on the bulb, water gets filled in the dropper. The rise of water in the dropper is due to

(a) pressure of water.

(b) gravity of the earth.

(c) shape of rubber bulb

(d) atmospheric pressure

A rocket has been fired upwards to launch a satellite in its orbit. Name the two forces acting on the rocket immediately after leaving the launching pad.

Name the forces acting on a plastic bucket containing water held above ground level in your hand. Discuss why the forces acting on the bucket do not bring a change in its state of motion.

An inflated balloon was pressed against a wall after it has been rubbed with a piece of synthetic cloth. It was found that the balloon sticks to the wall. What force might be responsible for the attraction between the balloon and the wall?

A blacksmith hammers a hot piece of iron while making a tool. How does the force due to hammering affect the piece of iron?

In the following situations identify the agent exerting the force and the object on which it acts. State the effect of the force in each case.

(a) Squeezing a piece of lemon between the fingers to extract its juice.

(b) Taking out paste from a toothpaste tube.

(c) A load suspended from a spring while its other end is on a hook fixed to a wall.

(d) An athlete making a high jump to clear the bar at a certain height.

An archer stretches her bow while taking aim at the target. She then releases the arrow, which begins to move towards the target. Based on this information fill up the gaps in the following statements using the following terms.

muscular, contact, non-contact, gravity, friction, shape, attraction

(a) To stretch the bow, the archer applies a force that causes a change in its _______.

(b) The force applied by the archer to stretch the bow is an example of ________force.

(c) The type of force responsible for a change in the state of motion of the arrow is an example of a _______force.

(d) While the arrow moves towards its target, the forces acting on it are due to ________and that due to________of air.

Fill in the blanks in the following statements.

(a) To draw water from a well we have to _________at the rope.

(b) A charged body ________an uncharged body towards it.

(c) To move a loaded trolley we have to _________it.

(d) The north pole of a magnet ________the north pole of another magnet.

Give two examples of situations in which applied force causes a change in the shape of an object.

Give two examples each of situations in which you push or pull to change the state of motion of objects.