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16
MCQ (Single Correct Answer)

In a shotput event an athlete throws the shotput of mass 10 kg with an initial speed of $$1 \mathrm{~m} \mathrm{~s}^{-1}$$ at $$45^{\circ}$$ from a height 1.5 m above ground. Assuming air resistance to be negligible and acceleration due to gravity to be $$10 \mathrm{~m} \mathrm{~s}^{-2}$$, the kinetic energy of the shotput when it just reaches the ground will be

A
2.5 J
B
5.0 J
C
52.5 J
D
155.0 J
17
MCQ (Single Correct Answer)

Which of the diagrams in figure 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
18
MCQ (Single Correct Answer)

A cricket ball of mass 150 g moving with a speed of $$126 \mathrm{~km} / \mathrm{h}$$ 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 0.001 s , the force that the batsman had to apply to hold the bat firmly at its place would be

A
10.5 N
B
21 N
C
1.05 $$\times$$ 10$$^4$$ N
D
2.1 $$\times$$ 10$$^4$$ N
19
MCQ (Multiple Correct Answer)

A man of mass $$m$$, standing at the bottom of the staircase, of height $$L$$ climbs it and stands at its top.

A
Work done by all forces on man is equal to the rise in potential energy mgL
B
Work done by all forces on man is zero
C
Work done by the gravitational force on man is mgL
D
The reaction force from a step does not do work because the point of application of the force does not move while the force exists
20
MCQ (Multiple Correct Answer)

A bullet of mass $$m$$ fired at $$30^{\circ}$$ to the horizontal leaves the barrel of the gun with a velocity $$v$$. The bullet hits a soft target at a height $$h$$ above the ground while it is moving downward and emerge out with half the kinetic energy it had before hitting the target.

Which of the following statements are correct in respect of bullet after it emerges out of the target?

A
The velocity of the bullet will be reduced to half its initial value
B
The velocity of the bullet will be more than half of its earlier velocity
C
The bullet will continue to move along the same parabolic path
D
The bullet will move in a different parabolic path
E
The bullet will fall vertically downward after hitting the target
F
The internal energy of the particles of the target will increase