## The Cart and The Brick

### Part B

A GIF Animation

Collisions between objects are governed by laws of momentum and
energy. When a collision occurs in an isolated system, the total
momentum of the system of objects is conserved. Provided that there
are no net external forces acting upon the objects, the momentum of
all objects before the collision equals the momentum of all objects
after the collision. If there are only two objects involved in the
collision, then the momentum lost by one object equals the momentum
gained by the other object.

The animation below portrays the collision between a 1.0-kg cart
and a 2-kg dropped brick. It will be assumed that there are no net
external forces acting upon the two objects involved in the
collision. The only net force acting upon the two objects (the cart
and the dropped brick) are internal forces - the force of friction
between the cart and the dropped brick. The before- and
after-collision velocities and momentum are shown in the data
tables.

In the collision between the cart and the dropped brick, total
system momentum is conserved. Before the collision, the momentum of
the cart is 60 kg*cm/s and the momentum of the dropped brick is 0
kg*cm/s; the total system momentum is 60 kg*cm/s. After the
collision, the momentum of the cart is 20.0 kg*cm/s and the momentum
of the dropped brick is 40.0 kg*cm/s; the total system momentum is 60
kg*cm/s. The momentum of the cart-dropped brick system is conserved.
The momentum lost by the cart (40 kg*cm/s) is gained by the dropped
brick.

For more information on physical descriptions of motion, visit
The Physics Classroom. Detailed
information is available there on the following topics:

Momentum
Momentum Conservation
Principle

Isolated
Systems

Momentum Conservation
in Collisions

Other animations can be seen at the Multimedia
Physics Studios.

© Tom Henderson, 1996-2007

All Rights Reserved