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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

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

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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