Chapter 10 - Force and Types of Force
1. Choose the term to fill in the blanks.
(a) …… has to be applied to change the ….. of a …… object.
(moving, direction, force)
Ans: force, direction, moving
(b) When an elephant drags a wooden log over the land, the forces that are applied on the log are …… , ……. and …….. .
(muscular force, mechanical force, gravitational force, frictional force)
Ans: muscular force, gravitational force, frictional force
(c) A ball was set rolling on a large table. If its …… is to be changed, a …….. will have to be applied on it.
(force, motion, gravitation)
Ans: motion, force
(d) The force of friction always acts …….. the motion.
(along, against)
Ans: against
2. Match the following :
| Group ‘A’ | Group ‘B’ |
|---|---|
(i) An ox pulling a cart | (a) Magnetic force |
(ii) Lifting a heavy iron object with a crane | (b) Electrostatic force |
(iii) Weighing with a spring balance | (c) Muscular force |
(iv) Applying brakes to a bicycle | (d) Gravitational force |
(v) Picking up pieces of paper with a plastic scale | (e) Frictional force |
Ans:
| Group ‘A’ | Group ‘B’ |
|---|---|
(i) An ox pulling a cart | (c) Muscular force |
(ii) Lifting a heavy iron object with a crane | (a) Magnetic force |
(iii) Weighing with a spring balance | (d) Gravitational force |
(iv) Applying brakes to a bicycle | (e) Frictional force |
(v) Picking up pieces of paper with a plastic scale | (b) Electrostatic force |
3. One or more forces are acting in the following examples. Name them.
(a) An object falling from a tall building ….
Ans: Gravitational force
(b) An aeroplane flying in sky ….
Ans: Mechanical and Gravitational force
(c) Squeezing sugarcane juice with a squeezer ….…. .
Ans: Muscular force
(d) Winnowing foodgrain ……. .
Ans: Muscular and Gravitational force
4. Explain in your own words giving one example each.
a. Muscular force:
Ans: The force applied by the action of muscles in our body is termed as muscular force.
For example, when you pick up a book placed on the table using your hands, you apply muscular force.
b. Gravitational force:
Ans: It is the force that is exerted by the earth on every object that is near or on its surface.
For example, an apple falling from a tree branch towards the ground is due to gravitational force.
c. Mechanical force:
Ans: The force generated by a machine is known as mechanical force.
For example, When a car starts, the engine exerts mechanical force on the tyres, allowing the vehicle to accelerate. As a result, the car moves due to the force generated by the machine on the tyres.
d. Electrostatic force
Ans: The force that exists either between the two charged bodies or between a charged and an uncharged body
The charged scale, for example, attracts the pieces of paper through a non-contact force known as electrostatic force.
e. The force of friction::
Ans: The force that acts opposite to the direction of motion of a body is known as the force of friction.
For example, a ball rolling on the ground eventually stops because of the frictional force acting between the ground and the ball.
f. Magnetic force:
Ans: The force exerted by a magnet is known as magnetic force.
For example, the separation of iron stuff from junk is done with the help of magnetic force.
5. Why?
(a) Machines are oiled from time to time.
Ans: A machine is oiled from time to time to reduce friction between its body parts. By doing so, the life span of a machine increases.
(b) An object thrown upwards comes down after reaching a point.
Ans: An object thrown upwards comes down after reaching a point. This is because of the Earth’s gravitational pull.
(c) Powder is sprinkled on a carrom board.
Ans: Powder is sprinkled on a carrom board to reduce friction between the striker and the carrom coins and the carrom board. The powder smooths the surface of the board, so the striker and coins can move easily on it.
(d) The ramp at a railway station has a rough surface.
Ans: The ramp at a railway station has a rough surface, so that the friction between our feet and the ground is enough for us to walk comfortably and without tripping.
6. In what way are we different?
(a) Muscular force and mechanical force.
Ans:
| Muscular force | Mechanical force |
|---|---|
(i) The force applied with the help of muscles is called muscular force. | (i) The force applied by means of a machine is called mechanical force. |
(ii) For example, to lift something with our hands, we apply muscular force. | (ii) For example, to lift any heavy object, cranes apply mechanical force. |
(b) The force of friction and gravitational force.
Ans:
| The force of friction | Gravitational force |
|---|---|
(i) When two surfaces rub against each other, the force of friction comes into play which always acts against the direction of motion. | (i) The force applied by the earth to pull objects towards itself is called gravitational force. |
(ii) For example, a ball rolling over a flat ground eventually stops because of the frictional force acting between the ground and the ball. | (ii) For example, the gravitational force operates between the sun and the planets in the solar system. Because of this, the planets revolve around the sun. |
7. Write answers to the following questions in your own words.
(a) What are the things that can be done by applying force ?
Ans: The following things can be done by applying force:
(i) It can move a body initially at rest.
(ii) It can bring a moving body to rest.
(iii) It can change the direction of a moving body.
(iv) It can change the speed of a moving body.
(v) It has the ability to alter the shape of a body.
(vi) It can change the size of a body.
(b) What is meant by weight ?
Ans: Weight is the force exerted on a body due to the gravitational pull of the earth.
(c) Which machines run on muscular force ?
Ans: Machines that run on muscular force are:
(i) Bicycle
(ii) Rickshaw
(iii) Hand pump
(iv) Stitching machine
(v) Hand cart
8. Solve the following crossword puzzle.
Down :
(1) ……. force is to be applied to push a scooter that has failed.
Ans: muscular
(2) ……….. force can be used to pick up scattered pins.
Ans: magnetic
Across :
(1) A ………. pulls an iron nail towards itself.
Ans: magnet
(3) ………. force was used when the farm was ploughed with a tractor.
Ans: mechanical
(4) It is due to the force of …………. that raindrops fall to the ground.
Ans: Gravity
