Effect of Nature of Surface on Friction

Q.

What is the limiting force of friction?

Q.

Why does the friction increase when two surfaces are pressed against each other harder? [3 MARKS]

Q. Does the smoothness of the sliding surface affect friction?

Q. If the roughness of a surface increases then the frictional force ________.

1. will increase
2. will decrease
3. cannot be predicted.
4. will remain the same

Q. On a slippery road we generally take small foot steps because

1. we want to reduce our normal reaction force.
2. slippery road cannot produce large frictional force.
3. small foot steps produce small frictional force.
4. roughness of the road can be increased by taking small foot steps.

Q. Fighter jets have a streamlined body in order to ___________ .

1. reduce cost
2. reduce air resistance
3. improve aesthetics
4. None of the above

Q.

Friction is large for____________surfaces and small for____________surfaces.

Q. Two identical balls A & B are placed on two different horizontal surfaces C & D respectively. When the same amount of force is applied on both the balls, B moves farther than ball A. Choose the correct statement.

1. Friction between A and C is greater than B and D.
2. Friction between B and D is greater than A and C.
3. Friction between B and D is lesser than A and C.
4. Friction between A and C is lesser than B and D.

Q. A 5 Kg box is kept on a rough horizontal surface and another 1 kg box is kept on a smooth horizontal surface. Which of the following statement is true?

1. 5 Kg box has higher frictional force compared to 1 kg box.
2. 1 Kg box has higher frictional force compared to 5 kg box.
3. Both boxes have zero frictional forces.
4. Frictional force on the blocks will depend on the roughness and smoothness of the contacting surfaces.

Q. Two bodies of masses 4 kg 9 kg are moving on a rough horizontal surface with same speed. If the coefficient of friction for them is same then ratio of dis†an ce travelled by the two bodies before coming rest

Q.

How does friction depend on the surface of bodies in contact?

Q. Statement 1: Two smooth surfaces generally offer friction due to adhesion.

Statement 2: Two rough surfaces generally offer friction due to interlocking of irregularities.

1. Only statement 2 is correct
2. Both statements are correct
3. Only statement 1 is correct
4. Both statements are incorrect

Q. Statement 1: Two smooth surfaces generally offer friction due to adhesion.

Statement 2: Two rough surfaces generally offer friction due to interlocking of irregularities.

1. Only statement 1 is correct
2. Only statement 2 is correct
3. Both statements are correct
4. Both statements are incorrect

Q. Statement 1: Two smooth surfaces generally offer friction due to adhesion.

Statement 2: Two rough surfaces generally offer friction due to interlocking of irregularities.

1. Only statement 2 is correct
2. Both statements are correct
3. Both statements are incorrect
4. Only statement 1 is correct

Q. You spill a bucket of soapy water on a marble floor accidentally. Would it be easier or more difficult for you to walk on the floor?
[2 marks]

Q. Which among the following helps to reduce the friction between two surfaces?

1. Grooves
2. Polishing
3. Lubricants
4. Ball bearings

Q. Person A slides a heavy box on a smooth surface andPerson B has to slide same box on a rough force. Who'll have to apply a larger force and why?

Q.

John carried out an experiment to find out how different surfaces (P, Q, R and S) affect the distance a car travelling at 50 km/h needed to stop once the brakes are applied. The results are shown below.
$\begin{array}{ccccc}Typeofroadsurfaces& P& Q& R& S\\ Stoppingdistance& 18& 15& 19& 27\end{array}$
Which type of road will provide the most friction for the car to stop ?

1. P

2. Q

3. R

4. S

Q. A stationary block remains stationary even after applying a horizontal force. This means that frictional force is applied force.

1. equal to
2. greater than
3. less than

Q.

Answer the following questions :

A. Using a horizontal force of 200 N, we are moving a wooden cabinet across a floor at a constant velocity. What is the friction force that is being exerted on the cabinet?

B. Ram's bike is moving with a speed of 90 km/hr. In traffic he had to reduce his speed to 30 Km/hr. By how much will the force of friction change? [3 MARKS]

Q. Frictional force depends on:

1. roughness of the surfaces
2. shape of the surfaces
3. colour of the surfaces
4. area of the surfaces

Q.

What is friction

Q. Two highly polished metal surfaces have negligible friction between them.

1. True
2. False

Q.

Friction can be reduced to zero by applying lots of lubricants between surfaces.

1. rubbing of hands gainst each other

2. rubbing of eraser against paper

Q. Which of the following objects have smooth surfaces?

1. Glass tumbler
2. Silk cloth
3. Rusty iron piece
4. Plane mirror
5. Sandpaper
6. Uneven rock
7. Marble tile
8. Granite tile

Q. Sprinkling powder on a carrom board increases friction.

1. True
2. False

Q. John carried out an experiment to find out how different road surfaces (P, Q, R and S) affect the stopping distance of a car travelling at 50 km/h. The result is tabulated below.

$\begin{array}{ccccc}\text{Type of road surface}& P& Q& R& S\\ \text{Stopping distance (m)}& 18& 15& 19& 27\end{array}$

Which surface provides maximum frictional force?

1. Q
2. R
3. S
4. P

Q.

Four identical wooden blocks are slid with same initial velocities on four different horizontal surfaces - sand, concrete, clay and ice. On which of these surfaces, will the distance travelled be maximum?

1. Sand

2. Ice

3. Concrete

4. Clay