# NCERT Physics Class 11 Exemplar Ch 6 Work Energy and Power Part 3

Q 13. Which of the diagrams shown in Fig. represents variation of total mechanical energy of a pendulum oscillating in air as function of time?

(a)

(b)

(c)

(d)

Ans: (d)

Q 14. A mass of 5 kg is moving along a circular path of radius 1 m. If the mass moves with 300 revolutions per minute, its kinetic energy would be

(a)

(b)

(c)

(d)

Ans: (a)

Q 15. A raindrop falling from a height h above ground, attains a near terminal velocity when it has fallen through a height (3/4)h. Which of the diagrams shown in Fig. correctly shows the change in kinetic and potential energy of the drop during its fall up to the ground?

(a)

(b)

(c)

(d)

Ans: (b)

Q 16. In a shotput event an athlete throws the shotput of mass 10 kg with an initial speed of at from a height 1.5 m above ground. Assuming air resistance to be negligible and acceleration due to gravity to be , the kinetic energy of the shotput when it just reaches the ground will be

(a)

(b)

(c)

(d)

Ans: (d)

Q 17. Which of the diagrams in Fig. Correctly shows the change in kinetic energy of an iron sphere falling freely in a lake having sufficient depth to impart it a terminal velocity?

(a)

(b)

(c)

(d)

Ans: (b)

Q 18. A cricket ball of mass 150 g moving with a speed of 126 km/h hits at the middle of the bat, held firmly at its position by the batsman. The ball moves straight back to the bowler after hitting the bat. Assuming that collision between ball and bat is completely elastic and the two remain in contact for 0.001s, the force that the batsman had to apply to hold the bat firmly at its place would be

(a)

(b)

(c)

(d)

Ans: (c)

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