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A rocket consumes fuel at the rate of 100 kg/s and
the exhaust gases are ejected at a speed of 45 km/s.
The rocket would then experience a thrust (in MN)
equal to

2.25

4.5

0.45

0.225

Which of the following statements is wrong?

impulse equals the change in momentum

action and reaction are equal and opposite and hence cancel each other

the momentum of a system of two bodies is conserved when there is no external force acting on either body

the work done on a particle must equal change in its kinetic energy.

Two balls of mass 2 kg and 4 kg respectively are connected to the two ends of a spring. The balls are pressed together and placed on a smooth table. When released, the lighter ball moves with an acceleration of 2 m/s2. The acceleration of the heavier ball will be

0.5 m/s2

1 m/s2

2 m/s2

4 m/s2

While launching a rocket of mass 2 * 104 kg, a force of 5 * 105 is applied for 20 seconds. The velocity attained by the rocket at the end of 20 seconds would be

350 m/s

500 m/s

750 m/s

900 m/s

A ball weighing 0.01 kg hits a hard surface vertically with a speed of 5 m/s and rebounds with the same speed. The ball remains in contact with the surface for 0.01 second. The average force exerted by the surface on the ball in Newton’s is

0.1

1.0

5.0

10.0

The weight of a pile driver is 250 kg and it drops freely 10 m on the top of a pile weighing 1000 kg. If the pile is driven by 10 cm, the common velocity of the pile driver and the pile after the impact is (Take g= 9.8 m/s2.)

1.4 m/s

2.8 m/s

3.5 m/s

4.2 m/s

A body of mass m moving with velocity v makes a head-on elastic collision with a stationary body of mass nm. The fraction of the incident energy transferred to the body at rest is

n/n+1

n/(n+1)2

2n/(n+1)2

4n/(n+1)2

A ball of mass m and velocity v strikes a wall at right angles and rebounds with undiminished speed. During the time t of collision, average force exerted on the wall is

mv2/2

mv2/t

mv2/2t

2mv/t

/

25 mkgf

40 mkgf

60 mkgf

75 mkgf

A mass m1 hanging at the end of a string moves a mass m2 along the surface of a smooth table. If mass m2 on the table is doubled, the tension in the string is increased by one-half. The ratio m1/m2is

2/3

1/2

3/2

2

2.25

4.5

0.45

0.225

Which of the following statements is wrong?

impulse equals the change in momentum

action and reaction are equal and opposite and hence cancel each other

the momentum of a system of two bodies is conserved when there is no external force acting on either body

the work done on a particle must equal change in its kinetic energy.

Two balls of mass 2 kg and 4 kg respectively are connected to the two ends of a spring. The balls are pressed together and placed on a smooth table. When released, the lighter ball moves with an acceleration of 2 m/s2. The acceleration of the heavier ball will be

0.5 m/s2

1 m/s2

2 m/s2

4 m/s2

While launching a rocket of mass 2 * 104 kg, a force of 5 * 105 is applied for 20 seconds. The velocity attained by the rocket at the end of 20 seconds would be

350 m/s

500 m/s

750 m/s

900 m/s

A ball weighing 0.01 kg hits a hard surface vertically with a speed of 5 m/s and rebounds with the same speed. The ball remains in contact with the surface for 0.01 second. The average force exerted by the surface on the ball in Newton’s is

0.1

1.0

5.0

10.0

The weight of a pile driver is 250 kg and it drops freely 10 m on the top of a pile weighing 1000 kg. If the pile is driven by 10 cm, the common velocity of the pile driver and the pile after the impact is (Take g= 9.8 m/s2.)

1.4 m/s

2.8 m/s

3.5 m/s

4.2 m/s

A body of mass m moving with velocity v makes a head-on elastic collision with a stationary body of mass nm. The fraction of the incident energy transferred to the body at rest is

n/n+1

n/(n+1)2

2n/(n+1)2

4n/(n+1)2

A ball of mass m and velocity v strikes a wall at right angles and rebounds with undiminished speed. During the time t of collision, average force exerted on the wall is

mv2/2

mv2/t

mv2/2t

2mv/t

/

25 mkgf

40 mkgf

60 mkgf

75 mkgf

A mass m1 hanging at the end of a string moves a mass m2 along the surface of a smooth table. If mass m2 on the table is doubled, the tension in the string is increased by one-half. The ratio m1/m2is

2/3

1/2

3/2

2

Quetions are on rocket propulsion, collision, and energy. It can help you in revising all thar you have studied in motion

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