A coin is dropped in a lift. It takes time t1 to reach the floor when lift is stationary. It takes time t2 when the lift is moving up with constant acceleration. Then:
(1) t1 > t2
(2) t2 > t1
(3) t1 = t2
(4) t1 >> t2
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.
2.
3.
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)
(3) Zero
(4) 2 Mg