Question

Starting from rest, you push your 1000kg car over a 5m distance, on an horizontal ground, applying a horizontal 400N force.a) What is the car kinetic energy change?b) What is its final velocity at the end of the 5 meters displacement? Disregard any friction force.

Answer 1

a) From the work-kinetic energy theorem, we get:

$$\Delta KE=W=Fd=400\ N\cdot5\ m=2000\ J.$$

b)

$$KE_f=\dfrac{1}{2}mv_f^2=W,$$ $$v_f=\sqrt{\dfrac{2W}{m}}=\sqrt{\dfrac{2\cdot2000\ J}{1000\ kg}}=2\ \dfrac{m}{s}.$$