A 2000 kg car is rolling at 3 m/s. You would like to stop the car by firing a 10 kg blob of sticky clay at it. How fast should you fire the clay? How much energy is required to accelerate the

clay to this speed?

1 answer

to stop a moving object, a force with the same magnitude should be applied at opposite direction.therefore:

momentum of car + momentum of clay = 0
momentum of car = - momentum of clay

mass of car x speed of car = mass of clay x speed of clay
speed of clay = (mass of car x speed of car) / mass of clay
speed of clay = 2000kg x 3m/s / 10kg
=600m/s

kinetic energy = momentum^2 / 2mass
=6000^2/2(10)
= 1.8 x 10^6 J