Question

a bullet with a mass of 50 gr and a velocity of 200m/s is stopped by a wall. How much has the internal energy of the bullet and the wall have increased

Answer 1

The internal energy increase (the energy of the wall increase and the kinetic energy of the bullet decrease):

$$\Delta E = \frac {m \cdot v ^ {2}}{2} = \frac {0.05 \cdot 200 ^ {2}}{2} = 1000 \mathrm{~J}.$$

Answer: 1000 Joules.