Question

1. if rooney is cross - country skiing, has a mass of 56.7 kg, and her kinetic energy is 367.4 j, what is her speed?

28.4 m/s
6.5 m/s
5.7 m/s
3.6 m/s

Explanation:

Step1: Recall kinetic energy formula

The kinetic energy formula is $KE = \frac{1}{2}mv^2$, where $KE$ is kinetic energy, $m$ is mass, and $v$ is speed.

Step2: Rearrange for speed

Isolate $v$: $v = \sqrt{\frac{2KE}{m}}$

Step3: Substitute given values

Substitute $KE=367.4\ \text{J}$, $m=56.7\ \text{kg}$:
$v = \sqrt{\frac{2\times367.4}{56.7}}$

Step4: Calculate the result

First compute numerator: $2\times367.4 = 734.8$
Then divide: $\frac{734.8}{56.7} \approx 12.96$
Take square root: $\sqrt{12.96} = 3.6\ \text{m/s}$

Answer:

D. 3.6 m/s