Energy Lab: How High Does It Go?
The cart has a spring in it with three settings. You fire it up a slope and mark how high it gets, and the site draws the graph. Then you make the cart heavier and fire it with the same spring. There is nothing to calculate anywhere in this lab. You work in a group the site draws for you, and each of you is given a job.
Before you are put in a groupfour questions
Answer these on your own. They are not marked and they are not part of the fifty points. When you have answered all four the page shows you every answer worked through, and the lab opens after that.
1. You push the spring in at the back of the cart and lock it. What have you done?
Pushing the spring in takes work, and the spring keeps it until it is let go. Nothing is moving yet, so there is no motion to speak of, and the cart has not changed its mass.
2. The cart is fired up the slope. At the highest point it reaches, it stops for an instant before coming back down. At that instant, what has become of the energy the spring gave it?
The cart is not moving at that instant, so none of it is in motion. It climbed to get there, and that is where the energy went.
3. You fire the cart on the same spring setting twice: once on its own, and once with both masses on it. Which goes higher?
The spring gives the same amount both times. A heavier cart takes more of it to lift through the same height, so the same amount does not lift it as far.
4. For every run in Part 2, which two things does your group write down?
Those two are what the graph is made of. If one of them goes missing for a run, that run cannot go on the graph at all, so say them out loud and have somebody repeat them back.
Not open yet
Type your class code above. The lab opens when Mr. Tuna opens it, and your group and your job appear here as soon as he draws them.
What each group needs
- one dynamics track, with an end stop at the bottom
- one Smart Cart. The button at the back fires its spring, and the spring has three settings
- the two cart masses
- a meter stick, and sticky notes to mark the track with
- a piece of string long enough to reach across the track
- something steady to raise one end of the track with
The three jobs, one each. The site gives you yours.
- PASCO Capstone operator
- Runs the software and reads out whatever the group asks for.
- Physical set-up
- Sets up whatever the group decides to set up, and changes it when they decide to change it. Two people may share this job.
- Data recorder and team leader
- Writes down every number as it is called out and repeats it back. Decides what the group does next, and opens the next part when this one is done.
1. Fire it along the flat track10 points
Leave the track flat on the table for this part. Put the cart on it with the spring end facing down the track.
Fire the cart on the lowest spring setting and watch it. Then fire it on the highest setting. Write down what was different about the two. Say where you think the cart got its motion from, given that nobody pushed it.10 pts
2. Fire it up the hill20 points
Raise one end of the track and leave it at that height for the whole of this part. The cart starts at the bottom every time, and one of you catches it on the way back down.
- Fire the cart up the slope on setting one. Mark the highest point it reaches with a sticky note.
- Measure how high that mark is above the table, in centimeters. Write it down beside the setting.
- Do the same on setting two, then on setting three.
- Then do all three again, twice more, so every setting has three runs.
(a)Put your nine runs in. The site draws the graph. Put the setting across the bottom and the height up the side.14 pts
(b)Describe your graph in words. Does the cart get higher on a stronger spring, and is each step up about the same size? Say what the spring gave the cart, and what the cart turned it into on the way up.6 pts
3. The level line10 points
Hold the string across the track so that it is level, at the height the cart reached on setting two. Tape it or have somebody hold each end.
Fire the cart on setting two again and check that it still reaches the string. Now put both cart masses on and fire it on setting two, the same spring as before. Say whether it reached the string. Then say why the same spring did not do the same job, in your own words.10 pts
4. Agree on what you found10 points
This part belongs to all of you.
(a)With the masses still on, say first which setting you think will get the cart back up to the string. Write that down before you try it. Then try it and write down what happened.5 pts
(b)Write your group’s conclusion. Say what the spring gave the cart, what the cart had instead of it at the top, and what the extra mass changed.5 pts