Work, Energy and Power

The average kinetic energy of a hydrogen gas molecule at NTP will be (Boltzmann's  constant k = 138 x 10^-23 J/K)

• 0.186 × 10^-20 J

• 0.372 × 10^-20 J

• 0.56 × 10^-20 J

• 5.6 × 10^-20 J

The height of a water fall is 84 m. Assuming that the entire kinetic energy of falling water is converted into heat, the rise in temperature of the water will be

• 0.196°C

• 1.960°C

• 0.96°C

• 0.0196°C

A steel ball is dropped from a height h and it makes a perfectly elastic collision with a horizontal plane. Following its initial release, it will make periodic motion with frequency

• $2\mathrm{\pi }\sqrt{\frac{\mathrm{g}}{\mathrm{h}}}$

• $2\mathrm{\pi }\sqrt{\frac{\mathrm{h}}{\mathrm{g}}}$

• $\frac{1}{2}\sqrt{\frac{\mathrm{g}}{2\mathrm{h}}}$

• $\frac{1}{2}\sqrt{\frac{2\mathrm{h}}{\mathrm{g}}}$

Momentum of a body of mass 1 kg is 10 kg-m/s, then its kinetic energy will be

• 100 J

• 50 J

• 1000 J

• 200 J

If the heat of 110 J is added to a gaseous system, whose internal energy is 40 J. Then the amount of external work done is

• 140 J

• 70 J

• 110 J

• 150 J

A bomb of mass 16 kg at rest explodes into two pieces of masses 4 kg and 12 kg. The  velocity of the 12 kg mass is 4 ms^-1 . The kinetic energy of the other mass is

• 192 J

• 96 J

• 144 J

• 288 J

A particle is acted upon by a conservative force F = $\left(7\stackrel{\wedge }{\mathrm{i}} - 6\stackrel{\wedge }{\mathrm{j}}\right)$ N (no other force is acting on the particle). Under the influence of this force, particle moves from (0,0) to (-3m, 4m), then

• work done by the force is 3 J

• work done by the force is − 45 J

• at (0, 0) speed of the particle must be zero

• at (0, 0) speed of the particle must not be zero

If W₁ , W₂ and W₃ represent the work done in moving a particle from A to B along three different paths 1, 2 and 3 respectively in the gravitational field of a point mass m shown in the figure, find the correct relation between W₁ , W₂ and W₃ .

• W₁ > W₂ > W₃

• W₁ = W₂ = W₃

• W₁ < W₂ < W₃

• W₂ > W₁ > W₃

The potential energy of a certain spring when stretched through a distance x is 20 J. The amoµnt of work that must be done on this spring to stretch it through an additional distance $\frac{\mathrm{x}}{2}$ will be

• 20 J

• 25 J

• 5 J

• 15 J

The driver of a truck travelling with a velocity v suddenly notice a brick wall infront of him at a distance r. How the driver avoid himself by crashing into the wall ?

• By speeding up the truck

• By applying a brake

• By slowing down the truck

• By taking a circular turn