Speeds of the rolling ball at different points in this roller coaster track

  • #1
Ineedhelpwithphysics
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Homework Statement:
The image is below.
Relevant Equations:
Distance/time
Physics.png

For this question i tried to reason with my self that C was the fastest and A was the second fastest. B would be the third fastest and D would be the least fastest since the ball has to go up. I looked up the answer and it says that C is the fastest , B and D are equal, and A is the slowest. How is that possible if A is the slowest even though with D you have to go up. And any time you go up you lose speed.
Thank you for helping.
 

Answers and Replies

  • #2
hmmm27
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And any time you go up you lose speed.
What happens to your speed when you go down ?
What happens to your speed when you're on the same level ?
 
  • #3
berkeman
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Homework Statement:: The image is below.
Relevant Equations:: Distance/time

I looked up the answer and it says that C is the fastest , B and D are equal, and A is the slowest.
What are the gravitational potential energies (GPEs) at those points on the track, compared to each other? Remember that KE+PE should be constant unless there are losses (like air resistance).
 
  • #4
Ineedhelpwithphysics
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What happens to your speed when you go down ?
What happens to your speed when you're on the same level ?
Yes exactly so how is A the slowest if the ball is going down.
 
  • #5
Ineedhelpwithphysics
22
3
What are the gravitational potential energies (GPEs) at those points on the track, compared to each other? Remember that KE+PE should be constant unless there are losses (like air resistance).
I didn't learn gravitational potential energies I am in chapter 3 of paul hewitts conceptual physics book.
 
  • #6
hmmm27
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any time you go up you lose speed.
What happens to your speed when you go down ?
What happens to your speed when you're on the same level ?
Yes exactly so how is A the slowest if the ball is going down.
"Yes exactly" to what ? exactly.

The problem says "released", not "shoved", "pushed" or "shot". At point "O" its speed is zero. Do things slow down the farther they fall ?

Also, the problem is meant to be envisioned/answered without consideration for friction forces ; the ball's speed isn't being affected by the air and it's not rubbing against the track.
 
Last edited:
  • #7
haruspex
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Yes exactly so how is A the slowest if the ball is going down.
Going down means it is getting faster, not that it is already fast. And it can't be at the highest speed yet if it is still accelerating.
 

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