# COLLIDING TROLLEYS

## AIM

TO INVESTIGATE WHETHER TOTAL MOMENTUM IS CONSERVED DURING A COLLISION.

## INTRODUCTION

The law of conservation of momentum is that the total momentum of an object before an event is equal to after the event. The equation for momentum is:

Momentum (kg m/s) = Mass (kg) x speed (m/s)

## MATERIAL

Two dynamics trolleys

Electronic balance

Metre ruler
Ruler

Level benchtop

Piece of A4 paper

Several 1 kg masses to add to the trolleys

Two rubber bands tied together that will stretch to 20 cm quite easily

## METHOD

1. The piece of A4 paper was attached to the benchtop with masking tape. Two parallel lines were ruled on the paper, 20 cm apart.

2. The two trolleys were linked with the rubber bands.

3. The trolleys were pulled apart and were held with their front ends on the two lines.

4. The trolleys were released.

5. The distance from one line to the collision point (d1) were measured and the same for the other line (d2).

6. Various masses were added to one (or both) of the trolleys and the experiment was repeated.

## RESULTS

M 1: 0.2 kg
D 1: 0.1 m
M 1 x D 1 = 0.02

M 2: 0.2kg
D 2: 0.1 m
M 2 x D 2 = 0.02

(M1 × D1) – (M2 × D2) = 0

## DISSCUSSION

1 When the trolleys are released, do they travel towards each other for the same period of time? Explain.

Yes, They travel the same amount of time before colliding.

2 Is the magnitude of the force acting on each trolley the same? Explain.

Yes, the weight of the trolleys are the same, the rubber band gives them the same pull

and the gravitational pull is the same.

3 If both trolleys come to a stop after the collision, what was the final total momentum of the ‘system’? Explain.

0. Because they come to a stop after the collision and the momentum of a stationary

object is 0.

4 According to the last column of results, what was the initial total momentum of the ‘system’?

0. Because the object was originally stationary.

## CONCLUSION

The momentum of the trolley before collision and after collision is the same because the trolley was originally stationary and becomes stationary again after the collision.