Advantages of Friction

Q. A ball sliding on ground comes to rest after a while. Which force opposes its motion?

1. Gravitational force
2. Frictional force
3. Magnetic force
4. Muscular force

Q.

To sharpen the blade of a knife by rubbing it against a surface, which of the following will be most suitable?

1. stone

2. plastic block

3. wooden block

4. glass block

Q.

A boy rolls a rubber ball on a wooden surface. The ball travels a short distance before coming to rest. To make the same ball travel a longer distance before coming to rest, he may

1. Spread a carpet on the wooden surface.

2. Cover the ball with a piece of cloth

3. Sprinkle talcum powder on the wooden surface.

4. Sprinkle sand on the wooden surface

Q.

The force of friction is always disadvantageous.

1. True
2. False

Q.

Mention one way in which we make use of the heat produced by friction.

Q. The matchbox sides are made so rough in order to ___________ .

1. eliminate friction
2. hold matchsticks easily
3. increase friction
4. decrease friction

Q.

In which of the following situation friction is necessary?

1. Heating of a working mixer

2. Running of a water motor

3. Striking a matchstick

4. None of these

Q.

The statement given below is incorrect. Write the correct statement.

The tires of vehicles are provided with deep grooves so as to decrease friction between the road and the tires.

Q. When you rub your hands vigorously, your hands become hot because rubbing causes friction between the hands which in turn produces heat.

1. True
2. False

Q.

To increase friction between two bodies

1. their surface contact should be rough

2. the wight of the body should be more

3. both A and B

4. none of these

Q.

Why do we feel warm when we rub our hands together and touch our cheeks?

Q.

Which of the following options illustrate the positive effects of friction?

1. Magnetic force

2. Frictional force

3. Gravitational force

4. Air pressure

Q.

If we rub our palms, they become warm. Why?

Q.

When a log of wood cut with saw it becomes hot. Why?

Q. Friction is necessary in lighting a match stick.

1. False
2. True

Q. Friction is not required in heating an electric heater.

1. False
2. True

Q. Fill in the blanks:
More the roughness of a surface, greater is the ______.

Q.

In which of the following case(s) is friction a friend?

1. Heating of a working mixer

2. Noisy machines

3. Wearing of machines

4. Using pen for writing

Q.

Look at the pictures given below:

(a)

(b)

(c)

Identify the picture in which friction plays a helpful role.

1. A, B and C

2. A and B only

3. B and C only

4. A and C only

Q. In , friction is a friend.

1. wearing of machines
2. using pen for writing
3. noisy machines

Q. When we rub our hands together, frictional force give rise to .

1. light energy
2. heat energy
3. electrical energy
4. chemical energy

Q.

In case of ice skating, replacing ice surface with grass will make no difference.

1. True

2. False