John's mass is half teh mass of Jill. They both start walking and John moves twice as fast as Jill. what is

Question

the ration of the kinetic energy of Jill to the kinetic energy of John?

Answer 1

Let m= mass of Jill
m*1/2=mass of John

Let v=speed of Jill
2v=speed of John

The required general formula is:

Kinetic Energy=1/2mv^2

Kinetic Energy, KE, of Jill=1/2mv^2
Kinetic Energy, KE', of John=1/2m*1/2*(2v)^2

The ratio of KE to KE':

(1/2mv^2)/(1/2m*1/2*2^2v^2)

1/2mv^2 cancel out:

KE/KE'=1/2