Factors Affecting Friction

Q. $F_1$ is the force of friction on a box just before it starts sliding, and $F_2$ is the force of friction when it starts sliding. Which of the following is incorrect about $F_1$ and $F_2$?

1. $F_1$ is static friction, and $F_2$ is sliding friction.
2. $F_1$ > $F_2$
3. $F_1$ = $F_2$
4. $F_2$acts in same direction as $F_1$

Q.

Which of the following is not a lubricant?

1. None of these

2. Oil

3. Grease

4. Graphite

Q.

Neha has to push a light box and Sohit has to push a comparatively heavier box made of same material, on the same horizontal floor. What can we say about the forces applied by them?

1. It runs out of push

2. It runs out of electricity

3. Force of gravity made it slow

4. It rubs against the ice

Q.

A cube is pushed in such a way that it is sliding on a horizontal surface. Frictional force acting on the cube can be increased by:

1. Polishing the outer surface of the cube.

2. Adding wheels to the cube.

3. Applying lubricant between the cube and the surface.

4. Placing another identical cube on top of the cube.

Q. Friction depends on the following two factors:
(a) Materials of the body in ___.
(b) ___ of the two surfaces.

1. contact:roughness
2. fluids:volume
3. air:density
4. vacuum:mass

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.

Which of the following is a lubricant?

1. Sand

2. Salt

3. Grease

4. Rubber

Q. Applying lubricants to machines increases their efficiency.

1. Towards right

2. Towards left

Q.

Consider the following statements:

Statement 1: Friction is caused due to interlocking of irregularities present on the surfaces in contact.
Statement 2: Frictional force increases if the two surfaces are pressed harder.

Which of these statements is/are correct?

1. Only statement 1 is correct.

2. Only statement 2 is correct.

3. Both the statements are correct.

4. Neither of the statements is correct.

Q. Which of the following methods can be used to increase friction between two surfaces?

1. Applying lubricant between surfaces

2. Using powder between surfaces

3. Making the surfaces more irregular
4. Using ball bearings