Question

a boy and his skateboard have a combined mass of 65 kg. what is the speed of the boy and skateboard if they have a momentum of 275 kg·\frac{m}{s}?
0 m/s
0.24 m/s
4.2 m/s
8.5 m/s

Explanation:

Step1: Recall momentum formula

The formula for momentum is $p = mv$, where $p$ is momentum, $m$ is mass and $v$ is velocity (speed in this non - directional case). We need to solve for $v$, so we can re - arrange the formula to $v=\frac{p}{m}$.

Step2: Substitute given values

We are given that $p = 275\ kg\cdot\frac{m}{s}$ and $m = 65\ kg$. Substituting these values into the formula $v=\frac{p}{m}$, we get $v=\frac{275\ kg\cdot\frac{m}{s}}{65\ kg}$.

Step3: Calculate the speed

$v=\frac{275}{65}\ m/s\approx4.2\ m/s$.

Answer:

C. 4.2 m/s