A scooter starting from rest moves with constant acceleration for a time Δt₁ then with a constant velocity for the next Δt₂ and finally with a constant deceleration for the next Δt₃ to come to rest. A 500 N man sitting on the scooter behind the driver manages to stay at rest with respect to the scooter without touching any other part. The force exerted by the seat on the man is

1. 500 N throughout the journey

2. less than 500 N throughout the journey

3. more than 500 N throughout the journey

4. > 500 N for time Δt₁ and Δt₃ and 500 N for Δt₂

Consider the situation shown in the figure. The wall is smooth but the surfaces of \(A\) and \(B\) in contact are rough. The friction on \(B\) due to \(A\) in equilibrium:

Suppose all the surfaces in the previous problem are rough. The direction of friction on B due to A

1. is upward

2. is downward

3. is zero

4. depends on the masses of A and B

Previous problem: Consider the situation shown in the figure. The wall is smooth but the surfaces of A and B in contact are rough.

Two cars of unequal masses use similar tyres. If they are moving at the same initial speed, the minimum stopping distance

1. is smaller for the heavier car

2. is smaller for the lighter car

3. is the same for both cars

4. depends on the volume of the car

In order to stop a car in shortest distance on a horizontal road, one should:

A block A kept on an inclined surface just begins to slide if the inclination is 30°. The block is replaced by another block B and it is found that it just begins to slide if the inclination is 40°.

1. mass of A > mass of B

2. mass of A < mass of B

3. mass of A = mass of B

4. All the three are possible

A boy of mass M is applying a horizontal force to slide a box of mass M' on a rough horizontal surface. The coefficient of friction between the shoes of the boy and the floor is µ and that between the box and the floor is µ'. In which of the following cases it is certainly not possible to slide the box?

1. µ < µ’, M < M’

2. µ > µ’, M < M’

3. µ < µ', M'> M’

4. µ > µ', M > M’

Let \(F,F_N\) and \(f\) denote the magnitudes of the contact force, normal force and the friction exerted by one surface on the other kept in contact. If none of these is zero,

Choose the correct option:

The contact force exerted by a body A on another body B is equal to the normal force between the bodies. We conclude that

(a) the surfaces must be frictionless

(b) the force of friction between the bodies is zero

(c) the magnitude of normal force equals that of friction

(d) the bodies may be rough but they don’t slip on each other

Choose the correct option:

1. (a) and (b)

2. (b) and (c)

3. (b) and (d)

4. (a) and (c)

Mark the correct statements about the friction between two bodies.

Choose the correct option: