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Velocity-Time Graphs and Friction

  • Thread starter Mooshk
  • Start date
  • #1
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Homework Statement


An object moves up and down an inclined, frictionless surface.
1) Draw a Velocity-Time Graph of this situation.
2) If there was friction, how would it impact the graph?


Homework Equations


Ek = 1/2 m v^2
Eg = mgh
Ek = Eg
I don't think the equations are necessary in the solution, but I included these equations since energy must be conserved as the object moves on the surface, so the final and initial speeds must be the same too.


The Attempt at a Solution


Since the track is frictionless, acceleration should be constant. This means that the velocity graph should be linear with a constant slope. If friction is involved, it will oppose the direction of motion meaning the acceleration up the incline and down the incline will be different, meaning that friction works the same no matter if the object is moving upwards or downwards. So, the velocity graph will not be linear in shape. When the object moves downwards, it should speed up because the parallel component of the gravitational force is in that direction. In that case, the graph should look like a V. Is this correct?
 

Answers and Replies

  • #2
3,812
92
Since the track is frictionless, acceleration should be constant. This means that the velocity graph should be linear with a constant slope.
The magnitude of acceleration is constant in the first case, not the direction. If the body moves up again, the motion retards instead of getting accelerated.
 
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