Q1: 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.

Ans.

(a) apply force (lift)                 (b) attracts

(c) pull / push                          (d) repels.

Q2: 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

Ans.

(a) shape       

(b) muscular       

(c) non-contact       

(d) gravity, friction.

Q3: 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.

Ans.

 

S. No.

 

Agent exerting the force

 

Object on which it acts

 

Form of affect

(a)

Fingers

(i) Lemon as whole
(ii) Juice in side

Change in shape
Change in state of motion

(b)

Fingers

(i) Tube as whole
(ii) Paste in side

Change in shape Change in state of motion

(c)

Load

Spring

Change in shape

(d)

Ground from which athlete takes jump

Athlete itself

Change in state of motion

 

Q4: 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?

Ans. Electrostatic force.

Q5: 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.

Ans. (a) pressure of water.

Q6: What is force?

Ans. A push or pull on an object is called a force.

Q7: Has force only magnitude or both direction and magnitude?

Ans. Force has both magnitude and direction.

Q8: What is the necessary condition for a force to come into play.

Ans. At least two objects must interact for a force to come into play.

Q9: We know that a force applied on an object causes either a change in its state of motion or its shape. Different types of events are listed in the following table. Tell the type of effect in each case.

Force-Important-Questions-Q9

Ans.

Force-Important-Questions-Q9-Answer

Q10: Name the force responsible for the wearing out of bicycle tyres.

Ans. Force of friction.

Q11: What causes a change in the state of motion of an object?

Ans. The force of friction is responsible for change in the state of motion of an object.

Q12: What brings a ball rolling on the ground to rest gradually?

Ans. The force of friction between the surface of the ball and the ground brings the rolling ball to rest.

Q13: What force will you use to sort out pins easily from garbage? Whether it is a contact force or non-contact force?

Ans. Magnetic force act on to sort out pins and, it is a non-contact force.

Q14: When an object is thrown vertically upwards why does its speed decrease?

Ans. It’s speed decrease because the force of gravity opposes its upward motion.

Q15: What is electrostatic force?

Ans. The force exerted by a charged body on another charged or uncharged body is called electrostatic force.