Question

a 1200kg car is moving on the freeway at 30 m/s. (a) Find the magnitude of its momentum and its kinetic energy in SI units. (b) At what speed, in m/s, will the car's momentum be half of what it is in part (a). (c) At what speed, in m/s, will the cars kinetic energy be half of what it is in part (a)

Answer 1

momentum = m v = 1200 * 30 kg m/s

Ke = (1/2) m v^2 = 600 * 900 Joules

30/2 = 15

v^2 = (1/2)30^2 = 900/2 = 450
so
v = sqrt (450) = sqrt (9*50) = sqrt(3*3*5*5*2) = 15 sqrt 2
v = 21.2 m/s