NetLogo User Community Models

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Download If clicking does not initiate a download, try right clicking or control clicking and choosing "Save" or "Download".(The run link is disabled for this model because it was made in a version prior to NetLogo 6.0, which NetLogo Web requires.)

WHAT IS IT?

This is a simulation that illustrates inelastic collision between two trolleys (in this case two model cars A and B) moving over a low-friction surface [Friction is too small and therefore can be neglected]. This is a classic simulation that shows that the total momentum is conserved i.e. total momentum before collision = total momentum after collision.

The simulation can be used to alter the Mass and the Speed of the trolleys and also the direction of motion of trolley B. Direction of motion of trolley A before collision is fixed and is to the right.

HOW IT WORKS

Each trolly has a mass and a speed. The mass and the speed of the two trolleys can be set using the sliders. Trolley A always moves to the right whereas trolley B can move to the right or to the left as set by the user. After the two trolleys collide, they stick together and move as one (i.e. coalesce) but the total momentum before collision and the total momentum after collision always remains the same.

HOW TO USE IT

The Mass and the Speed of the trollys can be set using the following sliders:

   Mass_A: Mass of A
   Mass_B: Mass of B
   Speed_A: Speed of A
   Speed_B: Speed of B

The direction of the trolleys can be adjusted using the switch facing_each_other?
if facing_each_other? is true trolley B moves to the left otherwise it moves to the right.

Trolley A always moves to the right.

The monitors used in the simulator are as follows:

common-velocity: Shows the velocity of the two trolleys after collision. It is common
because the two trolleys coalesce and therefore they have the same velocity. Also note that we have used velocity and not speed because it also shows the direction. If the two trolleys after the collision move to the left, the velocity is negative -- if they move to the right, the common-velocity is positive.

   |Momentum of A before collision|: Magintude of the momentum of A before collision
   |Momentum of B before collision|: Magintude of the momentum of B before collision

THINGS TO NOTICE

See what happens if they have the same magnitude of the momentum before collision. For instance if Mass_A = 3 Kg, Speed_A = 5 m/s, Mass_B = 5 Kg and Speed_B = 3 m/s.
Check what happens when they are moving in the same direction and when they are moving in the opposite direction.

THINGS TO TRY

Try out all possible options:
*Keep one trolley at rest and the other moving
*Make them move towards each other
*Make them move in the same direction
In each case check whether the common velocity you calculate matches with that of ours. Also see how the momentum changes in each case.

EXTENDING THE MODEL

Since it is an inelastic collision, total kinetic energy is not conserved rather upon collision some energy will be lost as thermal energy and sound energy. These effects might be included in the extension of the model.