Second Law of Motion

Q. A block of mass $m$ is placed in contact with one end of a smooth tube of mass $M$ (see Fig.). A horizontal force $F$ acts on the tube in each case (i) and (ii). Then, immediately after applying force, the acceleration of $m$ and $M$ are:
\( M \) \( M \) (ii)

1. Force on $m$ is $\frac{mF}{M+m}$ in (ii)
2. $a_m=a_M=\frac{F}{M+m}$ in (ii)
3. $a_m=a_M=\frac{F}{M+m}$ in (i)
4. $a_m=0$ and $a_M=\frac{F}{M}$ in (i)

Q.

A rocket with a lift-off mass $3.5\times {10}^{4}kg$ is blasted upwards with an initial acceleration of $10m/s^2$. Then the initial thrust of the blast is

1. 

2. 

3. 

4. 

Q.

If the force on a rocket moving with a velocity of 300 m/s is 210 N, then the rate of combustion of the fuel is

1. 0.07 kg/s

2. 1.4 kg/s

3. 10.7 kg/s

4. 0.7 kg/s

Q.

A 500 kg rocket can be accelerated at a constant rate from rest to 1800 km/h in 2 sec. What is the magnitude of the required net force?

1. 450, 000 N

2. 12, 000 N

3. 125, 000 N

4. 18, 00, 000 N

Q.

A 5kg block is tied to a 1m string and is rotated with a constant angular velocity of 2 rad/sec in the horizontal plane. Find the linear momentum of the block.

1. 10 N

2. 5 m/s

3. 2.5 N

4. 10 kg m/s

Q. A car moving at a speed of 30 kilo meters per hour is brought to a halt in 8 metres by applying brakes. If the same car is moving at 60 km. per hour, it can be brought to a halt with same breaking power in

1. 16 metres
2. 24 metres
3. 32 metres
4. 8 metres

Q.

On forgetting his 25th anniversary, Vijay as a present from his wife, receives a shoe of 0.5 kg thrown at him with 10 m/s velocity. Find the momentum of assault.

1. 0.5 N

2. 5 kg m/s

3. 10 Kg m/s

4. 5 N

Q.

The net force on a body is varying with time as (2t + 3) N. Find the change in momentum of the body after 2 secs?

1. 5 kg m/s

2. 2 kg m/s

3. 10 kg m/s

4. 0 kg m/s

Q.

A machine gun fires a bullet of mass 40 g with a velocity of $1200m{s}^{-1}$. The gun can exert a maximum force of 144 N on the bullet. How many bullets can it fire per second at the most?
(AIEEE 2004)

1. Two

2. Four

3. One

4. Three

Q.

In a rocket of mass 1000 kg fuel is consumed at a rate of 40 kg/s. The velocity of the gases ejected from the rocket is $5\times {10}^4$ m/s. The thrust on the rocket is

1. 

2. 

3. 

4.