Question

A 200-g Nerf dart is shot from a dart gun with a kinetic energy of 3.60 J. What was the initial of the speed dart?

Answer 1

By definition, the kinetic energy is

$$K = \dfrac{mv^2}{2}$$

where $m = 200g = 0.2kg$ is the mass of the dart, and $v$ is its speed. Since $K = 3.6J$, obtain the following speed:

$$v = \sqrt{\dfrac{2K}{m}}\\ v = \sqrt{\dfrac{2\cdot 3.6}{0.2}} = 6m/s$$

Answer. 6m/s.