Positions Versus time on an incline

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Homework Help Overview

The discussion revolves around the motion of a block sliding up and down a frictionless incline, with a focus on the position versus time graph that best represents this motion. The original poster describes their reasoning regarding the expected graph shape and relates it to concepts of projectile motion.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to determine the correct graphical representation of the block's position over time, questioning whether it resembles projectile motion. They express confusion over feedback received from an online homework system.
  • Some participants seek clarification on the original poster's understanding of the problem and the specifics of the graphs provided.
  • Questions arise regarding the initial velocity of the block and its implications for the graph's slope.

Discussion Status

The conversation is ongoing, with participants exploring different interpretations of the problem and the associated graphs. Some guidance has been offered regarding the relationship between the slope of the position-time graph and velocity, but no consensus has been reached on the correct graph representation.

Contextual Notes

The original poster mentions that incorrect answers lead to point deductions in their online homework, indicating a high-stakes environment for their responses. There is also a note about a potential misunderstanding of the question's wording.

myeeth22
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The initial position of the block is the origin; i.e., x = 0 at t = 0 . Consider down the track to be the positive x-direction. A block with an initial velocity v0 slides up and back down a frictionless incline. Which graph best represents a description the position of the block versus time?

There's several graphs, some sinusoidal, some completely flat, some like absolute value, etc. There are also qa semicircle shaped one, which is what I picked. #10 on this (https://web2.ph.utexas.edu/~turner/classes/303K/1011Spring/oldmidterm%2001.pdf) has an image of each graph.

It would make sense to me that this graph would look like a projectile motion graph, since the velocity decreases due to gravity as the object slides up the ramp, eventually comes to a stop, and slide/falls back down, accelerating due to gravity. Apparently this isn't correct. Is this somehow different from projectile motion?
 
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Hello ME22, welcome to PF :smile: !

Please do use the template. We are not allowed to help you if you delete it.
It's not clear what you are asking. You have an answer sheet pdf with no semicircular picture on it. The picture number 1. is marked as "correct" and has the features you describe. Why do you say "apparently this is not correct"?
 
myeeth22 said:
The initial position of the block is the origin; i.e., x = 0 at t = 0 . Consider down the track to be the positive x-direction. A block with an initial velocity v0 slides up and back down a frictionless incline. Which graph best represents a description the position of the block versus time?

There's several graphs, some sinusoidal, some completely flat, some like absolute value, etc. There are also qa semicircle shaped one, which is what I picked. #10 on this (https://web2.ph.utexas.edu/~turner/classes/303K/1011Spring/oldmidterm%2001.pdf) has an image of each graph.

It would make sense to me that this graph would look like a projectile motion graph, since the velocity decreases due to gravity as the object slides up the ramp, eventually comes to a stop, and slide/falls back down, accelerating due to gravity. Apparently this isn't correct. Is this somehow different from projectile motion?
BvU said:
Hello ME22, welcome to PF :smile: !

Please do use the template. We are not allowed to help you if you delete it.
It's not clear what you are asking. You have an answer sheet pdf with no semicircular picture on it. The picture number 1. is marked as "correct" and has the features you describe. Why do you say "apparently this is not correct"?

My bad. Here's a reposted version

Homework Statement


The initial position of the block is the origin; i.e., x = 0 at t = 0 . Consider down the track to be the positive x-direction. A block with an initial velocity v0 slides up and back down a frictionless incline. Which graph best represents a description the position of the block versus time?

Homework Equations


Concept Question

The Attempt at a Solution


It would make sense to me that this graph would look like a projectile motion graph, since the velocity decreases due to gravity as the object slides up the ramp, eventually comes to a stop, and slide/falls back down, accelerating due to gravity. Apparently this isn't correct. Is this somehow different from projectile motion?It's online HW. When I plug the right number in (multiple choice) I'm told I'm wrong. I lose points every time I answer incorrectly, so I'd completely lost as to what I'm missing.
 
As it turns out, the question was inverted. I'll talk to my teacher about it the morning. I was worried I was totally missing the question!
 
myeeth22 said:
Consider down the track to be the positive x-direction. A block with an initial velocity v0 slides up and back down a frictionless incline.

Is the initial velocity positive or negative?

Remember that the slope of the position-time graph equals the velocity.
 

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