On a stationary sailboat, the air is blown at the sails from a fan attached to the boat. The boat will:

1. remain stationary

2. spin around

3. move in a direction opposite to that in which air is blown

4. move in the direction in which the air is blown

A man is standing on a spring platform. The reading of the spring balance is \(60\ \text{kg-wt}\). If a man jumps off the platform, then the reading of the spring balance:

1. first increases, then decreases to zero.

2. decreases.

3. increases.

4. remains the same.

A body of mass \(5\ \text{kg}\) is suspended by a spring balance on a smooth inclined plane as shown in the figure. The spring balance measures:

1. \(50\ \text{N}\)
2. \(25\ \text{N}\)
3. \(500\ \text{N}\)
4. \(10\ \text{N}\)

A lift is going up. The total mass of the lift and the passenger is \(1500\) kg. The lift's speed varies as shown in the graph. The tension in the rope pulling the lift at \(t=11^{\text{th}}\) s will be:

      
1. \(17400\) N
2. \(14700\) N
3. \(12000\) N
4. Zero

A player caught a cricket ball of mass \(150\ \text{g}\) moving at a rate of \(20\ \text{m/s}\). If the catching process is completed in \(0.1\ \text{s}\), then the force of the blow exerted by the ball on the hands of the player is:

1. \(0.3\ \text{N}\)
2. \(30\ \text{N}\)
3. \(300\ \text{N}\)
4. \(3000\ \text{N}\)

A rocket has a mass of 100 kg. 90% of this is fuel. It ejects fuel vapours at the rate of 1 kg/sec with a velocity of 500 m/sec relative to the rocket. It is supposed that the rocket is outside the gravitational field. The initial upthrust on the rocket when it just starts moving upwards is:

1. Zero

2. 500 N

3. 1000 N

4. 2000 N

In which of the following cases, a force will not be required to keep the particle in the given motion?
(A) The particle is going in a circle.
(B) The particle is going along a straight line.
(C) The momentum of the particle is constant.
(D) The acceleration of the particle is constant.

Choose the correct option from given ones:
1. (A) and (B)
2. (A) and (D)
3. (B) and (C)
4. (C) and (D)

A ball of mass 150g starts moving with an acceleration of 20 m/s² when hit by a force, which acts on it for 0.1 sec. The impulsive force is:

1. 0.5 N-s

2. 0.1 N-s

3. 0.3 N-s

4. 1.2 N-s

A body, whose momentum is constant, must have a constant: 

1. force.

2. velocity.

3. acceleration.

4. All of these

Rocket engines lift a rocket from the earth surface because hot gases with high velocity:

1. push against the earth.

2. push against the air.

3. react against the rocket and push it up.

4. heat up the air which lifts the rocket.