Question

A pinball bangs against a bumper, giving the ball a speed of 42 cm/s. If the ball has a mss of 50.0 g, what is the ball's kinetic energy in joules?

Answer 1

`0.0050625J = 5.0625*10^(-3) J = 5.06*10^(-3) J`

Explanation:

The equation for kinetic energy is `E_k = (mv^2)/2`

Next, we must put our values into standard units, so `"cm s"^(-1)` becomes `"m s"^(-1)`, and `"g"` becomes `"kg"`.

To convert `42"cm s"^(-1)` to `"m s"^(-1)`, we divide by 100, and we get `0.42"cm s"^(-1)`.

To convert `50"g"` to `"kg"`, we divide by 1,000 and we get `"0 05"kg"`.

Now we put our number into the equation, and get `(0.05*0.42^2)/2 = 0.0050625J = 5.0625*10^(-3) J = 5.06*10^(-3) J`.