107
NEWTON’S SECOND LAW
This states that when a force acts on an object, it makes the
object change speed or direction. As the two cars collide,
the front of each car exerts a force on the other car, slowing
it down. The dummies inside are slowed down as they
experience the force of the seatbelt.NEWTON’S THIRD LAW
The third law of motion says that when a force acts on
an object, the object reacts by pulling or pushing back
with equal force, but in the opposite direction. So, it
is impossible for one car to push on the other without
experiencing a push back with equal force.(^2) Collision When two cars
collide, kinetic energy is
converted to other forms
of energy, such as heat and
sound, as the fronts of the
cars crumple. This is called
an inelastic collision.
(^3) Momentum If a heavy lorry
collides with a car, the lorry’s
greater momentum pushes the
car along for some distance, but
cars of equal weight and speed
are halted, as their equal but
opposite momenta cancel out.
2
3
2
3
106_107_Dynamics.indd 107 03/01/19 12:10 PM