Question

A car traveling at 60 mph has how much more energy than a car going at 20 mph? KE increases by a factor of _____. 1/3 1/9 3 9

Answer 1

Answer: 9

Step-by-step explanation:

The kinetic energy of a car is given by

`E_k = (1)/(2)mv^2`

where

m is the mass of the car

v is its speed

In this case, the kinetic energy of the car moving at 20 mph is

`K_1 = (1)/(2)m(20)^2`

While the kinetic energy of the car moving at 60 mph is (assuming same mass m)

`K_2 = (1)/(2)m(60)^2`

The ratio between the two kinetic energies is:

`(K_2)/(K_1)=((1)/(2)m(60)^2)/((1)/(2)m(20)^2)=(60^2)/(20^2)=((60)/(20))^2=3^2=9`

So, the faster car has a kinetic energy which is 9 times more than the slower car.