A mass m moving horizontally (along the x-axis) with velocity $$v$$ collides and sticks to a mass of 3m moving vertically upwards (along the y-axis) with velocity 2$$v$$. The final velocity of the combination is

The potential energy of a system increases if work is done

Force F on a particle moving in a straight line varies with distance d as shown in figure.


The work done on the particle during its displacement of 12 m is

A body projected vertically from the earth reaches a height equal to earth's radius before returning to the earth. The power exerted by the gravitational force is greatest