Calculate the kinetic energies of the following objects moving at the given speeds.

Question

(a) a 120 kg football linebacker running at 9.00 m/s

 

(b) a 4.40 gram ball at 580 m/s

Answer 1

Hello, you can calculate KE by using the following calculation:

KE (in Joules) = 1/2 (mass)(velocity)²

Problem 1) In this problem, Mass = 120 kg; Velocity = 9.00 m/s; Therefore KE (J) = 1/2 (120kg)(9.00m/s)²

You can do the math and be sure to square the velocity.

Problem 2) In this problem, Mass = 4.40 g; Velocity = 580 m/s; Therefore in order to get the mass to be in kg instead of grams, you need to do the following:

4.40g_ x 1 kg_ = weight in kg

1 1000 g

You can take that mass in kg and plug it into KE (J) = 1/2 (weight in kg)(580 m/s)²

You can do the math and be sure to square the velocity.

Your answers will be in Joules = (kg)(m²/s²)

I hope this is helpful. If you have more questions, please let me know!