Nature of Surfaces in Contact

Q.

Which will cause more friction: a rough surface or a smooth surface? Why?

Q.

What is Friction?

Q.

A good lubricant must have __________.

Q.

Which is easier to hold in hand : a kulhar (earthen pot) or a glass tumbler ? Why ?

Q.

Ball rolling on a flat surface slows down because of friction.

1. True

2. False

Q.

A sandpaper is an example of smooth texture.

1. True
2. False

Q. Friction in fluids is called:​

1. Force
2. Pressure
3. Drag
4. Thrust

Q.

Least amount of friction is required in which of the following sports?

1. Rubbing of hands

2. Rubbing of glass

3. Rubbing of sand paper

4. Rubbing of woollen clothes

Q.

Why do kabaddi players rub their hands with dry soil ?

Q.

Explain how the nature of the two surfaces in contact affects friction between them.?

Q.

Give reasons for the following: why does a car skid on a wet road?

Q.

How does a lubricant help in reducing friction?

Q. A ball rolling on a grass field slows down due to:

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

Q.

Two boys are riding their bicycles on the same concrete road. One has new tyres on his bicycle while the other has tyres that are old and used. Which of them is more likely to skid while moving through a patch of the road which has lubricating oil spilt over it?

Q.

Car wheels often spin on icy roads. Explain why.

Q. Which of the following will produce the maximum friction?
(a) rubbing of sand paper on glazed paper
(b) rubbing of sand paper on glass table top
(c) rubbing of sand paper on aluminium frame
(d) rubbing of sand paper on sand paper

Q. When a pencil cell is released from a certain point on an inclined wooden board, it travels a distance of 35 cm on floor A before it comes to rest. When the same pencil cell is released from the same point on the same inclined board, it travles a distance of 20 cm on floor B before coming to rest. Which floor, A or B, offers greater friction? Give reason for your answer.

Q. Why is talcum powder sprinkled on carrom board?

1. To maintain friction
2. To decrease friction
3. To decrease friction to zero
4. To increase friction

Q.

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

1. True

2. False

Q. A body is moving in a constant state of motion on rolling on ground
A)Friction is acting in the same direction
B)Friction is absent
C)Friction is greater
D)All of these

Q.

Name the force which increases when the two surfaces in contact are made more rough.

Q.

A person has applied some mustard oil on his hands. Which of the following objects will become most difficult for him to hold in his hand?
(a) Earthen cup(kulhar)
(b) thermocol tumbler
(c) glass tumbler
(d) wooden cup

Q.

Question 3
Alida runs her toy car on a dry marble floor, wet marble floor, newspaper and towel spread on the floor. The force of friction acting on the car on different surfaces in increasing order will be
(a) wet marble floor, dry marble floor, newspaper and towel.
(b) newspaper, towel, dry marble floor, wet marble floor.
(c) towel, newspaper, dry marble floor, wet marble floor
(d) wet marble floor, dry marble floor, towel, newspaper

Q.

You spill a bucket of soapy water on a marble floor accidentally. Would it make it easier or more difficult for you to walk on the floor? Why?

Q.

Assuming that a toy car is pushed with the same force, on which of the following surfaces would it travel the farthest?

1. Polished marble

2. Carpet

3. Cemented floor

4. Sandpaper

Q.

John carried out an experiment to find out how different surfaces (P, Q, R and S) affect the braking efficiency of a car traveling at $50km/h$. The results are shown below.
$\begin{array}{ccccc}\text{Type of road surfaces}& P& Q& R& S\\ \text{Stopping distance}& 18m& 15m& 19m& 27m\end{array}$
Which type of road will provide the greatest frictional force for the car to stop?

1. P

2. R

3. Q

4. S

Q.

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

1. True

2. False

Q.

How to reduce friction?

Q.

It is dangerous to drive on roads during rain. Give reason.

Q.

Give any two examples where we need higher friction.