Tag: physics

Questions Related to physics

Friction depends upon ................. of surfaces.

physics friction increasing and reducing friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it

  1. mass.

  2. nature of body.

  3. both A & B

  4. none

Show answer
Correct Option: C
Explanation:

Friction depends upon mass and nature of the body of surfaces.
Friction depends partly on the smoothness of the contacting surfaces, a greater force being needed to move two surfaces past one another if they are rough than if they are smooth. However, friction decreases with smoothness only to a degree; friction actually increases between two extremely smooth surfaces because of increased attractive electrostatic forces between their atoms. 
Friction does not depend on the amount of surface area in contact between the moving bodies or (within certain limits) on the relative speed of the bodies. It does, however, depend on the magnitude of the forces holding the bodies together. 
When a body is moving over a horizontal surface, it presses down against the surface with a force equal to its weight, i.e., to the pull of gravity upon it; an increase in the weight of the body causes an increase in the amount of resistance offered to the relative motion of all the surfaces in contact.

Graphite powder is used in machines to _________.

physics friction increasing and reducing friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it

  1. enhance friction

  2. enhance profit

  3. reduce friction

  4. reduce efficiency

Show answer
Correct Option: C
Explanation:

Graphite powder is used in machines to reduce friction
Graphite is the only non-metal element that is a good conductor of electricity. Crystal structures rarely occur and easily break down. This is the reason for the material's greasy feeling despite being a dry lubricant.

Can friction ever be eliminated?

physics friction increasing and reducing friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it

  1. Yes

  2. No

  3. Sometimes

  4. Depends on the object in regard

Show answer
Correct Option: B
Explanation:

However smooth or polished a surface might be, it always has some irregularities. Thus, the friction can never be eliminated.

The substance that helps to ______ friction are called lubricants.

physics friction increasing and reducing friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it

  1. increase

  2. decrease

  3. create

  4. eliminate

Show answer
Correct Option: B
Explanation:

Oils, grease, graphite, etc., are examples of lubricants. These form a thin layer between the two surfaces in contact thus avoiding them from scrubbing directly against each other. This makes the movement smooth and reduces friction.

Why are the tyres of automobiles grooved?

physics friction increasing and reducing friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it

  1. To improve the design

  2. To increase friction

  3. To make it durable

  4. To make it strong

Show answer
Correct Option: B
Explanation:

If the tyres of automobiles were smooth, the friction produced would be minimal and thus, it would be difficult to stop or turn the automobile, increasing the risk of accidents. Hence, the tyres are grooved so as to increase the friction between the tyre and the surface of the road.

Kabaddi players rub their hands with soil so that they can :

physics friction increasing and reducing friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it

  1. make their skin dry

  2. moisture the hands

  3. get a better grip while holding the opponent

  4. soil the opponent

Show answer
Correct Option: C
Explanation:

By rubbing their hands with soil, they make their hands rough. A rough surface has more friction which enhances their grip while holding the opponent.

Which of the following are done to reduce friction?
a) Making grooves in the shoes
b) Polishing rough surfaces
c) Using wheels, ball bearings
d) Creating an air cushion

physics friction increasing and reducing friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it

  1. a, b and c

  2. c and d

  3. b, c and d

  4. All of the above

Show answer
Correct Option: C
Explanation:
Making grooves in the shoes increases friction.
Polishing rough surfaces makes it smooth, thus reducing friction. 
Wheels and ball bearings create rolling friction which has the least magnitude compared to sliding and static friction.
Air cushion makes a layer of air between two surfaces, which helps in reducing friction.

How do brake pads help in stopping an automobile?

physics friction increasing and reducing friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it

  1. Brake pads press on the wheel and increase friction.

  2. Due to braking, the air pressure increases and the wheels stop.

  3. Both A and B

  4. None of the above

Show answer
Correct Option: A
Explanation:

The brake pads press on the wheels and increase the friction since the surface of the brake pads and the wheels are irregular, and the rough surface increases friction that opposes the motion of the wheel.

Which of the following are done to increase friction?

physics friction increasing and reducing friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it

  1. Greasing the machines

  2. Treading the tyres

  3. Sprinkling powder on the carom board

  4. All of the above

Show answer
Correct Option: B
Explanation:

The tyres are treaded to make it rough so that the frictional force increases when it comes in contact with the road. 

All others are done to decrease friction.

The steps for decreasing friction includes:

physics friction increasing and reducing friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it

  1. ball bearing used in moving parts of a machine

  2. the streamlined shape of an aircraft

  3. the layer of air between the hull of a hovecraft

  4. none of these

Show answer
Correct Option: A,B,C
Explanation:

1) As rolling friction is less than sliding friction the shafts are fixed on ball bearing so that so that friction is reduced considerably.

2) The friction due to air is reduced by making the automobiles streamlined. Streamline shape allows more air and water to flow easily which offers least resistance.
3) Another way of reducing friction is to separate surfaces by air. This principle is used in hovecraft. The layer of air reduces friction allowing aircraft to move easily.