Physics Math

Question

An athlete with a mass of 64.0 kg is in a cross country race, and at one instant he has a speed of 4.50 m/s.

 

A.) What is his kinetic energy at this instant?

 

B.) If he wishes to double his speed to reach the finish line, his kinetic energy will change by what factor?

 

Answer 1

(A)

 

K = mv²/2 = (64.0 kg)(4.50 m/s)²/2 = ? J

 

(B)

 

K increases by a factor of 2² = 4.  You can see this if you replace v with 2v in the equation for K.