A bullet weighing 10 gm moves with a velocity of l km/sec. Its kinetic energy is (i) 5000 Nm (ii) 5000 kg.m (iii) 5000 J A. Only (ii) B. Both (i) and (iii) C. Both (ii) and (iii) D. All (i), (ii) and (iii)

The correct answer is: B. Both (i) and (iii).

The kinetic energy of an object is given by the formula:

$KE = \frac{1}{2}mv^2$

where $m$ is the mass of the object and $v$ is its velocity.

In this case, the mass of the bullet is 10 g = 0.01 kg and the velocity is 1 km/s = 1000 m/s. Substituting these values into the formula gives:

$KE = \frac{1}{2}(0.01 \text{ kg})(1000 \text{ m/s})^2 = 5000 \text{ J}$

Therefore, the kinetic energy of the bullet is 5000 J.

The units of kinetic energy are joules (J). 1 J is equal to 1 kg m$^2$/s$^2$. Therefore, options (i) and (iii) are correct. Option (ii) is incorrect because the units are not joules.