Question

A 1250-kg car moves at 20.0 m/s. How much work must be done on the car to increase its speed to 30.0 m/s.

Answer 1

3.13 x 10^5 J

Step-by-step explanation:

The work done increases the car's kinetic energy so that its new speed is 30 m/s. So, we set t, the net work required to increase the car's speed equal to the change in the car's kinetic energy.

Wnet = △K = Kf - Ki = 1/2mvf^2 - 1/2mvi^2 = 1/2m(vf^2-vi^2) = 1/2(1250kg)((30m/s)^2 - (20m/s)^2) = 3.13x10^5 J

Answer 2

312,497.5Joules

Step-by-step explanation:

Work done = force × distance

W = FS

Get the force

F = ma

F = 1250×9.8

F = 12250N

Get the distances using the equation of motion

v² = u² +2gS

30² =20²+2(9.8)S

900 =400+19.6S

900-400 =19.6S

500 = 19.6S

S = 500/19.6

S = 25.51m

Get the work done

Work done = 12250×25.51

Workdone = 312,497.5Joules