Question

A wagon with a width of 2.4 m, moving at a speed of 15 m per second, was shot through by a bullet perpendicular to the movement of the wagon. The distance between the two bullet holes in the wagon’s walls is 6 cm. What is the speed of the bullet ?

Answer 1

A wagon with a width of $2.4\,\mathrm{m}$, moving at a speed of $15\,\mathrm{m}$ per second, was shot through by a bullet perpendicular to the movement of the wagon. The distance between the two bullet holes in the wagon's walls is $6\,\mathrm{cm}$. What is the speed of the bullet?

The speed of bullet is:

$$v_b = \frac{S}{t}$$

where $S$ – is a wagon width.

During time $t$ a wagon will move at distance $d$:

$$t = \frac{d}{v_w}$$

So:

$$v_b = \frac{S}{\frac{d}{v_w}} = \frac{S v_w}{d}$$ $$v_b = \frac{2.4\,\mathrm{m} \times 15\,\mathrm{m/s}}{0.06\,\mathrm{m}} = 600\,\mathrm{m/s}$$

Answer: $v_b = 600\,\mathrm{m/s}$