Question

a) What is the kinetic energy of a 1500 kg car traveling at a speed of 30 m/s (65mph)?b) From what height should the car be dropped to have this same amount of kinetic energy just before impact?c) Does your answer to part b depend on the car's mass?

Answer 1

Answer:

a) 675000J

b) 45m

c) No

Explanation:

a) The car kinetic energy with such mass and speed is:

$E_k = \frac{mv^2}{2} = \frac{1500*30^2}{2} = 675000J$

b) For the car to have the same kinetic energy just before the impact, its potential energy before dropped must be as much as the kinetic energy

$E_p = E_k = 675000J$

$mgh = 675000$

$1500*10*h = 675000$

$h = \frac{675000}{15000} = 45m$

c) According to the conservation in energy

$E_p = E_k$

$mgh= \frac{mv^2}{2}$

$h = \frac{v^2}{2g}$

Since masses cancel out, the height does not depend on its mass.