Conservation of Momentum

Conservation of Momentum Aim: To prove that the conservation of momentum is true

Apparatus: A set of pendulums Stands String A battery An eraser A styrene foam sheet A ruler A speedometer

Diagram and method: For P before

Measure the speed with a speedometer (unit m/s). Take the value as velocity and multiple that by the mass of the pendulum (in kg). V does not vary with the mass of the pendulum so we did this with a 20g pendulum only for 5 times.

For P after

1 Conservation of momentum Natsuki Ikeda Measure the distance (x) the 2nd pendulum is thrown. We know that Vh=x/t, t= and h, which is the height from the ground to the bottom of 2nd pendulum is 0.8985m. Therefore t=0.428 and from that calculate Vh (horizontal velocity) and multiply that by the mass of 2nd pendulum in kg. We changed both 1st pendulum and 2nd pendulum and we tried every possible combination we can make from one 10g pendulum, two 20g pendulums, one 50g pendulum, two 100g pendulums and one 200g pendulum. For every combination, 5 trials were made.

Results: 1st pendulum P before Error (%) 2nd pendulum P after Error (%) 0.0228 20g 0.020654 0.168769 10g 0.0228 0.57 50g 0.019953 0.348387 0.0228 100g 0.025794 0.508546 0.0456 10g 0.022136 0.108423 0.0456 20g 0.035262 0.121907 20g 0.0456 0.57 50g 0.050467 0.171388 0.0456 100g 0.054206 0.271164 0.0456 200g 0.050935 0.514363 0.114 10g 0.024626 0.103086 0.114 20g 0.04257 0.110532 50g 0.57 0.114 100g 0.08715 0.189695 0.114 200g 0.101869 0.285005 0.228 10g 0.032009 0.092144 0.228 20g 0.060467 0.094287 100g 0.228 0.57 50g 0.096145 0.116401 0.228 100g 0.158879 0.129177 0.228 200g 0.190654 0.178196 200g 0.456 0.57 10g 0.03729 0.086976 0.456 20g 0.058505 0.095583 0.456 50g 0.106075 0.110713 0.456 100g 0.200467 0.113922

The red line is the theoretical data (P before=P after). Conclusion: P after is not only about 2nd pendulum but about 1st pendulum. After hitting 2nd pendulum, 1st pendulum moves back. So assume that I can add 1st pendulum’s momentum, I can say that P before=P after i.e. the conservation of momentum is true.

Evaluation: The results were not so reliable because R² value is so small, which is 0.2452. It means that the results are not precise at all. I didn’t consider or I didn’t even know about the other momentums and they seem to be quite big so maybe I had better consider about them, for example, the 1st pendulum’s moving back momentum.

3 Conservation of momentum Natsuki Ikeda