225. A spring scale in a stationary lift shows a reading of 60 kg for a man standing on it. If the lift starts descending at an acceleration of g/5, the scale reading would be

A. 48 kg

B. 60 kg

C. 72 kg

D. none of these.

226. A ball of mass 250 g moving on a smooth horizontal table with a velocity of 10 m/sec hits an identical stationary ball B on the table. If the impact is perfectly plastic, the velocity of the ball B just after impact would be

A. zero

B. 5 m/sec.

C. 10 m/sec.

D. none of these.

227. The mechanical advantage of an ideal machine is 100. For moving the local through 2 m, the effort moves through

A. 0.02 m

B. 2 ni

C. 2.5 m

D. 20 rn.

228. A projectile is thrown at an angle a to the horizontal with a velocity v. It will have the maximum centripetal acceleration

A. at the start

B. at the top of the trajectory

C. as it strikes the ground

D. else where.

229. A 50 kg boy climbs up a 8 An rope in'gymnasiam in 10 sec. The average power developed by the boy is approximately

A. 400 watts

B. 500 watts

C. 4000 watts

D. none of these.

230. A pilot flies a small plane in a vertical loop of radius r. At the top of its trajectory he experiences weightlessness. If the acceleration due to gravity is g, the speed of the plane at the top of its trajectory would be

A. zero

B. infinite

C.

D.

231. The displacement of a particle which moves along a straight line is given by S = 4t3 + 3t2 ? 10 where S is in meters and t is in seconds. The time taken by the particle to acquire a velocity of 18 m/sec from rest, is

A. ?2sec

B. 1 sec

C. 1.5 sec

D. 1.5 sec.

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