Momentum Lab, What It Takes to Stop Something
The simulations are on this page. Work down the page and use them as you go. Parts 3 and 4 ask you to say what you expect before you press Run, so write that down first. Nothing here is calculated. Describe what you see and record what the panel tells you.
1. Warm-up: land on three different things5 points
A person of 60 kilograms landing on something. The top bar is the motion that has to be taken away. The first slider changes how long the landing is allowed to last, and the second changes how fast the person arrives.
Loading the simulation. If it does not appear, open it on the topic page.
Move both sliders as far as they go, in both directions, and watch the picture and the three bars. Then write one sentence about what you noticed.5 pts
2. The one thing you get to choose15 points
The same landing, using the simulation in Part 1 above. Set Speed on arrival to 6 m/s and leave it there for the whole of this part.
(a)Move the stopping-time slider slowly from one end to the other. Say which bars change, which bar does not move at all, and what the word underneath the lander changes to on the way.7 pts
(b)Now set the stop to each of the three times in the table and fill the table in. Then say which of the three landings you would rather have, and name a real object that does the same job as the longest one.8 pts
| How long the stop takes | Force on you (N) | Times your own weight | The word under the lander |
|---|---|---|---|
| 0.40 s | |||
| 0.10 s | |||
| 0.02 s |
3. Two carts that stick together15 points
Two carts on a track. Cart A rolls in from the left and cart B waits. The sliders set the two masses and how fast A arrives, and the fourth slider chooses whether the carts stick together or bounce apart. Set Speed of A to 4 and leave it there for the rest of the lab.
Loading the simulation. If it does not appear, open it on the topic page.
(a)Set both masses to 3 and choose sticking. Before you press Run, write down how fast you think the pair will be moving afterward. Then run it and write what the panel says.7 pts
(b)Now set A to 1 and B to 6, still sticking, and run it again. Say which way the pair goes and whether it is faster or slower than before. Then read the two lines momentum before and momentum after in both runs and say what you notice about them.8 pts
4. Bouncing, and the number that never moves15 points
The same two carts, using the simulation in Part 3 above. Speed of A stays at 4. The last slider chooses whether the carts stick together or bounce apart.
(a)Set A to 1 and B to 6 and switch the last slider to bouncing. Describe what cart A does after the collision. Then switch back to sticking with the same masses and say what is different.7 pts
(b)Run all four settings in the table and fill it in. Then say what is the same in every single row, and what that tells you about a collision.8 pts
| Masses, A and B | Stick or bounce | Momentum before | Momentum after | A ends at (m/s) |
|---|---|---|---|---|
| 3 and 3 | stick | |||
| 3 and 3 | bounce | |||
| 1 and 6 | stick | |||
| 1 and 6 | bounce |