Question

how fast would an 82 kg man need to run in order to have the same kinetic energy as an 8.0 g bullet fired at 420 m/s ? express your answer with the appropriate units.

Answer 1

Answer: 4.14846 m/s

Step-by-step explanation:
The equation used to calculate the kinetic energy of an object is:

KE = (1/2) * mass * (velocity)^2

So for this, we need to find the KE of the bullet first.

KE_Bullet = (1/2) * .008kg * (420m/s)^2
KE_Bullet = 705.6 J

Now, since we want the guy running to have this same energy, we simply use the Bullet’s Kinect energy in our calculation.

705.6 J = (1/2) * (82kg) * (V_man m/s)^2

V_man = sqrt ((705.6 J * 2) / 82kg)
V_man = 4.14846 m/s

Hence, the velocity a 82kg man would need to reach to achieve the same kinetic energy as a 8g bullet fired at 420 m/s would be 4.14846 m/s.

Cheers.