Question

a tennis ball has a mass of 0.06kg and has kinetic energy of 2.94KJ when served. what is it's speed?

Answer 1

By defintion, the kinetic energy is given as follows:

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

where $m = 0.06kg$ is the mass, and $v$ is the speed of the ball. Expressing $v$ from this formula and substituting $K = 2.94\times 10^3J$, obtain:

$$v = \sqrt{\dfrac{2K}{m}}\\ v = \sqrt{\dfrac{2\cdot 2.94\times 10^3}{0.06}}\approx 313m/s$$

Answer. 313 m/s.