Question

question 3 of 25
a man with mass 82 kg runs at a speed of 2.8 m/s. how much kinetic energy does he have?
a. 642.9 j
b. 321.4 j
c. 114.8 j
d. 221.8 j

Explanation:

Step1: Recall the kinetic energy formula

The formula for kinetic energy is \( KE=\frac{1}{2}mv^{2} \), where \( m \) is mass and \( v \) is velocity.

Step2: Substitute the given values

Given \( m = 82\space kg \) and \( v=2.8\space m/s \).
Substitute into the formula: \( KE=\frac{1}{2}\times82\times(2.8)^{2} \).
First, calculate \( (2.8)^{2}=7.84 \).
Then, \( \frac{1}{2}\times82 = 41 \).
Finally, \( KE=41\times7.84=321.44\approx321.4\space J \).

Answer:

B. 321.4 J