A car travels east with speed 20 m/s and then travels west with the same speed

PHYSICS · Single correct · A Level · Physics · Mechanics and materials · Mechanics and materials

Problem

A car travels east with speed 20 m/s and then travels west with the same speed. If its initial momentum is

\mathbf{p}

and its initial kinetic energy is

K

, which option correctly states the momentum

\mathbf{p}'

and kinetic energy

K'

after the direction reversal? (a)

\mathbf{p}'=\mathbf{p},\;K'=K

(b)

\mathbf{p}'=-\mathbf{p},\;K'=-K

(c)

\mathbf{p}'=-\mathbf{p},\;K'=K

(d)

\mathbf{p}'=-2\mathbf{p},\;K'=2K