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Practice each question, then open the answer or worked solution.
A body is moving unidirectionally under the influence of a source of constant power supplying energy. Which of the diagrams shown in the figure correctly shows the displacement-time curve for its motion?
b)
Which of the diagrams shown in figure most closely shows the variation in kinetic energy of the earth as it moves once around the sun in its elliptical orbit?
d)
Which of the diagrams shown in the figure represents variations of the total mechanical energy of a pendulum oscillating in air as a function of time?
c)
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) 250π2
b) 100 π2
c) 5 π2
d) 0
Answer: a) 250π2
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 show correctly the change in kinetic and potential energy of the drop during its falls up to the ground?
b)
In a shotput event an athlete throws the shotput of mass 10 kg with an initial speed of 1 m/s at 45o from height 1.5 m above ground. Assuming air resistance to be negligible and acceleration due to gravity to be 10 m/s2, 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
Answer: d) 155.0 J
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?
b)
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 0.001 sec, 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 × 104 N
d) 2.1 × 104 N
Answer: c) 1.05 × 104 N
Multiple Choice Questions IIA 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 zero
b) work done by all the force 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
b) work done by all the force on man is zero
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
A bullet of mass m fired at 30o 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 emerges 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?
e) the bullet will fall vertically downward after hitting the target
f) the internal energy of the particles of the target will increase
b) the velocity of the bullet will be more than half of its earlier velocity
d) the bullet will move in a different parabolic path
f) the internal energy of the particles of the target will increase