Going up and down with a Lift and Momentum Online Test

An isolated particle of mass M is moving in horizontal plane (x-y), along the x-axis, at a certain height above the ground. It suddenly explodes into two fragment of masses m/4 and 3m/4. An instant later, the smaller fragment is at y= + 15 cm. The larger fragment at this instant is at
Y=-5cm
Y=+20
Y=+5cm
Y=-20cm
Two blocks of masses 10 kg and 4 kg are connected by a spring of negligible mass placed on a frictionless horizontal surface. An impulse gives a velocity of 14 m/s to the heavier block in the direction of the lighter block. The velocity of the centre of mass is
30 m/s
20 m/s
10 m/s
5 m/s
A man stands on a spring weighing scale in a lift which carries him upwards with acceleration. The reading on the weighing scale will be
true weight of the man
lower than the true weight
greater than the true weight
zero
The tension in the cable supporting a lift moving upwards is twice the tension when the lift moves downwards. The acceleration of the lift is equal to
g
g/2
g/3
g/4
A 5 kg sphere is accelerated upward by a string whose breaking strength is 200 N. The maximum value of acceleration with which the sphere can move without breaking the string is
10 m/s2
20 m/s2
30 m/s2
50 m/s2
/
1.25 m/s2
2 m/s2
8 m/s2
12 m/s2
Two bodies P and Q have 50 N weights each. Body B is suspended from a spring balance whereas body Q is balanced in a physical balance. Both the balances are placed in an elevator which moves upwards with an acceleration g/2. Then:
weight of P increases and weight of Q decreases
weight of P increases and weight of Q remains the same
weight of P decrease and weight of Q remains the same
weight of P decreases and weight of Q increases
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
For the mass-pulley system depicted in Fig. 1.42, the mass m2 = 5 kg is placed on a smooth inclined plane of inclination a where as the mass m1 = 5 kg is hanging free. The acceleration of the system is 1.5 m/s2. If each mass is doubled, the acceleration will be
0.75 m/s2
1.5 m/s2
3.0 m/s2
An elevator weighs 2500 kg, and is moving vertically downwards with a constant acceleration. Starting from rest, it travels a distance of 35 meters during an interval of 10 seconds. The tension produced in the cable would be approximately
2325 kgf
2575 kgf
2500 kgf
2750 kgf
Description:

Numerical examples of various types, based on motion in a lift is given A few of them are based on conservation of momentum and are very helpful for AIEEE and IIT JEE preparation.

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Kajal Sengupta
Physics 9th to 12 th grade,CIE, Edexcel, AP, IB , CBSE, ICSE 87 Members Recommend
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