If the tension in the cable of 1000 kg elevator is 1000 kg weight, the elevator:

1. is accelerating upwards.

2. is accelerating downwards.

3. may be at rest or accelerating.

4. may be at rest or in uniform motion.

An object with a mass 10 kg moves at a constant velocity of 10 m/sec. A constant force then acts for 4 second on the object and gives it a speed of 2 m/sec in opposite direction. The acceleration produced in it, is 

1. 3 m/sec²

2. –3 m/sec²

3. 0.3 m/sec²

4. –0.3 m/sec²

A machine gun is mounted on a 2000 kg car on a horizontal frictionless surface. At some instant the gun fires bullets of mass 10 gm with a velocity of 500 m/sec with respect to the car. The number of bullets fired per second is ten. The average thrust on the system is 

1. 550 N

2. 50 N

3. 250 N

4. 250 dyne

In the above diagram, the acceleration of the car will be:

1. 0.25 m/sec²

2. 2.5 m/sec²

3. 5.0 m/sec²

4. 0.025 m/sec²

A particle of mass 0.3 kg is subjected to a force F = –kx with k = 15 N/m. What will be its initial acceleration if it is released from a point 20 cm away from the origin

1. 5 m/s²

2. 10 m/s²

3. 3 m/s²

4. 15 m/s²

An elevator weighing 6000 kg is pulled upward by a cable with an acceleration of 5 ms^–2. Taking g to be 10 ms^–2, then the tension in the cable is 

1. 6000 N

2. 9000 N

3. 60000 N

4. 90000 N

The ratio of the weight of a man in a stationary lift and when it is moving downward with uniform acceleration ‘a’ is 3 : 2. The value of ‘a’ is (g-Acceleration due to gravity of the earth) 

1. $\frac{3}{2}g$

2. $\frac{g}{3}$

3. $\frac{2}{3}g$

4. g

If force on a rocket having exhaust velocity of 300 m/sec is 210 N, then rate of combustion of the fuel is 

1. 0.7 kg/s

2. 1.4 kg/s

3. 0.07 kg/s

4. 10.7 kg/s

In an elevator moving vertically up with an acceleration g, the force exerted on the floor by a passenger of mass M is:

1. Mg

2. $\frac{1}{2}Mg$

3. Zero

4. 2 Mg

A 5000 kg rocket is set for vertical firing. The exhaust speed is 800 ms^–1. To give an initial upward acceleration of 20 ms^–2, the amount of gas ejected per second to supply the needed thrust will be (g = 10 ms^–2) 

1. 127.5 kg s^–1

2. 187.5 kg s^–1

3. 185.5 kg s^–1

4. 137.5 kg s^–1