• Friction (Set - III)
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Friction (Set - III)

Description: Friction � III
Number of Questions: 15
Created by:
Tags: Friction � III How Normal Force Affects Friction Wearing Effects of Friction Role of Friction in Motion Decreasing Friction by Using Lubricants Preference for Rolling Friction Against Sliding Friction Increasing Friction by Increasing Normal Force How to Reduce Fluid Friction How Smoothness Between Surfaces Affects Friction Cause of Friction Role of Friction in Daily Activities
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In which direction does force of friction act?

  1. Upward direction

  2. Downward direction

  3. The direction opposite to motion

  4. The direction of motion

Show answer
Correct Option: C
Explanation:

Friction opposes the relative motion between the two surfaces in contact, i.e. force of friction always acts in the direction opposite to the motion.

Why it is advised to apply machine oil or grease in the moving parts of a machine at regular intervals?

  1. To increase wearing by increasing friction

  2. To give it a shiny appearance

  3. To prevent wearing by decreasing friction

  4. To prevent wearing by increasing friction

Show answer
Correct Option: C
Explanation:

Machine oil or grease is used in moving parts of a machine in order to prevent wearing by decreasing friction.

It is difficult to drag a bucket full of water than an empty bucket because

  1. force of friction decreases as we drag a bucket full of water

  2. force of friction increases with the increase of normal force due to increased weight

  3. force of friction increases with the decrease of normal force due to increased weight

  4. force of friction is independent of the weight of the body

Show answer
Correct Option: B
Explanation:

The force of friction increases with increase of normal force. Therefore, it is difficult to drag a bucket full of water than an empty bucket.

Why is the shape of an aeroplane designed in a manner similar to the shape of a bird?

  1. To increase fluid friction

  2. To reduce fluid friction

  3. To maintain fluid friction

  4. To eliminate friction completely

Show answer
Correct Option: B
Explanation:

The shape of an aeroplane is designed in a manner similar to the shape of a bird to reduce fluid friction.

Why is lubricating oil used in the chain of a bicycle?

  1. To reduce friction

  2. To increase friction

  3. To produce excess heat

  4. To make it less energy efficient

Show answer
Correct Option: A
Explanation:

Lubricating oil is used in the chain of a bicycle to reduce friction.

Friction cannot be increased by

  1. providing better contact

  2. decreasing roughness

  3. increasing normal force

  4. both (1) and (2)

Show answer
Correct Option: B
Explanation:

Friction can be increased by providing better contact, increasing normal force or by increasing roughness. Friction decreases with decrease in roughness of the surface.

In which of the following activities does friction not play any role?

  1. Walking on a road

  2. Writing with a pen

  3. Reading a book

  4. Production of fire by striking a matchstick

Show answer
Correct Option: C
Explanation:

Friction comes into play when we walk, write or strike a matchstick against the rough surface.

What is the frictional force exerted by fluids called?

  1. Upthrust

  2. Sliding friction

  3. Drag

  4. Thrust

Show answer
Correct Option: C
Explanation:

The frictional force exerted by fluids is also called drag.

Why are brake pads used in the brake system of bicycles and automobiles?

  1. To reduce friction

  2. To increase friction

  3. To reduce normal force

  4. To prevent wearing of wheels

Show answer
Correct Option: B
Explanation:

We deliberately increase friction by using brake pads in the brake system of bicycles and automobiles. When you are riding a bicycle, the brake pads do not touch the wheels. But when you press the brake lever, these pads arrest the motion of the rim due to friction and the wheel stops moving.

Which of the following is the cause of friction between two surfaces?

  1. The force of attraction between the two surfaces in contact

  2. The interlocking of the irregularities of the surfaces in contact

  3. The force of repulsion between the two surfaces in contact

  4. The gravitational pull of the earth on the two surfaces

Show answer
Correct Option: B
Explanation:

Friction is caused due to the interlocking of irregularities of the surfaces in contact.

If your cycle is cleaned and oiled regularly, it will run smoothly and will last longer. Why?

  1. It increases friction in moving parts of the cycle.

  2. It reduces friction in moving parts of the cycle.

  3. It increases heating in the parts of the cycle.

  4. Both (1) and (3)

Show answer
Correct Option: B
Explanation:

Regular cleaning and oiling of your cycle reduces friction in moving parts of the cycle. As a result, it runs smoothly and lasts longer.

Which of the following statements is incorrect?

  1. Fluid friction can be minimised by giving suitable shapes to bodies moving in fluids.

  2. The soles of shoes and tyres of vehicles are treaded to decrease friction.

  3. In many machines, friction is reduced by using ball bearings.

  4. It is always easier to roll than to slide a body over another.

Show answer
Correct Option: B
Explanation:

The soles of shoes and tyres of vehicles are treaded to increase the grip.

Even a child can pull a piece of luggage fitted with rollers as compared to the one without rollers. Why?

  1. Because rolling friction is greater than the sliding friction

  2. Because rolling friction is smaller than the sliding friction

  3. Because rolling friction is equal to the sliding friction

  4. Because rolling friction and sliding friction oppose each other

Show answer
Correct Option: B
Explanation:

It is always easier to roll than to slide a body over another. It is convenient to pull a luggage fitted with rollers as rolling friction is smaller than the sliding friction.

On which of the following factors does frictional force not depend?

  1. The nature of surfaces in contact

  2. The state of smoothness of two surfaces in contact

  3. How hard the two surfaces press together

  4. The size of the contact area

Show answer
Correct Option: D
Explanation:

Frictional force does not depend upon the size of the contact area.

Why do we slip, when we accidently step on a banana peel?

  1. Because of increased friction

  2. Because of reduced friction

  3. Because of reduced gravitational force

  4. Because of upward reaction

Show answer
Correct Option: B
Explanation:

When we walk, we push the ground backwards with our foot. The tendency of the foot is to move in that direction. The force of friction opposes this tendency and acts in the opposite direction. This helps us to move forward. If the force of friction between our foot and floor is small, our foot may continue to move backwards. In that case, we may slip and fall.

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