Work Energy and...

An electron and a proton are moving under the influence of mutual forces. In calculating the change in the kinetic energy of the system during motion, one ignores the magnetic force of one on another. This is because,

A proton is kept at rest. A positively charged particle is released from rest at a distance d in its field. Consider two experiments: one in which the charged particle is also a proton and in another, a positron. In the same time t, the work done on the two moving charged particles is

A man squatting on the ground gets straight up and stand. The force of reaction of ground on the man during the process is

A bicyclist comes to a skidding stop in 10m. During this process, the force on the bicycle due to the road is 200N and is directly opposed to the motion. The work done by the cycle on the road is

A circket 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 s, the force that the batsman had to apply to hold the bat firmly at its place would be

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.

A body of mass 0.5kg travels in a straight line with velocity v = a\(x^{3\over2}\) where a = \(5m^{–1/2}s^{–1}\). The work done by the net force during its displacement from x = 0 to x = 2 m is

A body is initially at rest. It undergoes one dimensional motion with constant acceleration. The power delivered to it in time t is proportional to

A body is falling freely under the action of gravity alone in vacuum. Which of the following quantities remain constant during the fall?

During inelastic collision between two bodies, which of the following quantities always remain conserved?

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

In a shot put event an athlete throws the shot put of mass 10 kg with an initial speed of 1 m/s, at 45° from a height 1.5 m above ground. Assuming air resistance to be negligible and acceleration due to gravity to be 10 \(m/s^2\) , the kinetic energy of the shot put when it just reaches the ground will be

A bullet of mass m fired at 30° to the horizontal leaves the barrel of the gun with a velocity v. The bullet hits a soft target at 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?

(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.

A body is moving uni-directionally under the influence of a source of constant power. Its displacement in time t is proportional to :