Work, Energy and Power

If momentum is increased by 20%, then kinetic energy increases by

• 48 %

• 44 %

• 40 %

• 36 %

Two identical cylindrical vessels, with their bases at the same level, each contain a liquidof density ρ. The height of liquid in one vessel in h₁ and that in the other is h₂. The area of either base is A. What is the work done by gravity in equalizing the levels when the vessels are interconnected ?

In an inelastic collision an electron excites a hydrogen atom from its ground state to a M-shell state. A second electron collides instantaneously with the excited hydrogen atom in the M-shell state and ionizes it. At least how much energy the second electron transfers to the atom in the M-shell state ?

• + 3.4 eV

• + 1.51 eV

• − 3.4 eV

• − 1.51 eV

A cubical vessel of height 1 m is full of water. What is the amount of work done in pumping water out of the vessel ? (Take g = 10 m/s²)

• 1250 J

• 5000 J

• 1000 J

• 2500 J

A body of mass 6 kg is acted upon by a force which causes a displacement in it given by $\mathrm{x} = \frac{{\mathrm{t}}^2}{4}$metre, where t is the time in second. The work done by the force in 2 s is

• 12 J

• 9 J

• 6 J

• 3 J

A spherical ball A of mass 4 kg, moving along a straight line strikes another spherical ball B of mass 1 kg at rest. After the collision, A and B move with velocities v₁ ms^-1 and v₂ ms^-1 respectively making angles of 30° and 60° with respect to the original direction of motion of A. The ratio $\frac{{\mathrm{v}}_1}{{\mathrm{v}}_2}$ will be

• $\frac{\sqrt{3}}{4}$

• $\frac{4}{\sqrt{3}}$

• $\frac{1}{\sqrt{3}}$

• $\sqrt{3}$

An electric bulb marked as 50 W-200 V is connected across a 100 V supply. The present power of the bulb is

• 37.5 W

• 25 W

• 12.5 W

• 10 W

A uniform force of (3i + j) N acts on a particle of mass 2 kg. Hence the particle is displaced from position (2i + k) m to position ( 4i + 3j - k) m. The work done by the force on the particle is

• 9 J

• 6 J

• 13 J

• 15 J

A gas is taken through the cycle A → B → C → A, as shown. What is the net work done by the gas ?

• 2000 J

• 1000 J

• Zero

• − 2000 J

Consider a black body radiation in a cubical box at absolute temperature T. If the length of each side of the box is doubled and the temperature of the walls of the box and that of the radiation is halved, then the total energy

• halves

• doubles

• quadruples

• remains the same