Solving Velocity of a Box Off a Ramp

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Homework Help Overview

The discussion revolves around calculating the velocity of a box as it leaves a frictionless ramp. Participants are exploring the effects of gravity and the forces acting on the box during its motion along the ramp.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants are attempting to determine the appropriate distance to use in the velocity equation and question the forces acting on the box, including gravity and normal force. There is also discussion about the effects of the initial push and the direction of acceleration.

Discussion Status

The conversation is active, with participants questioning assumptions about the forces involved and the calculations needed. Some guidance has been offered regarding the relevance of the initial push and the need to consider forces as vectors, but no consensus has been reached on the calculations themselves.

Contextual Notes

There is uncertainty regarding the mass of the box, which is not provided, and participants are considering it as an arbitrary variable. The discussion also involves clarifying the definitions of terms like "fixed" and "frictionless" in the context of the ramp.

goonking
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Homework Statement



http://imgur.com/VwoDF58

Homework Equations


How would I calculate the velocity the box gets off the ramp?

I believe I need to use Vf = Vo + 2 a x

a is gravity so it is -9.8, correct?

but what do i put in as x? 5, which is the length of the ramp, or 4, the base, or 3 the height?
 
Last edited:
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The ramp is fixed and frictionless, right?

goonking said:
a is gravity so it is -9.8, correct?
Is gravity the only force acting on the box? In which direction is it accelerating?

goonking said:
but what do i put in as x? 5, which is the length of the ramp, or 4, the base, or 3 the height?
What is the distance the box travels?
 

Nathanael said:
The ramp is fixed and frictionless, right?Is gravity the only force acting on the box? In which direction is it accelerating?What is the distance the box travels?
I'm not sure what you mean by fixed, but it is friction less.

the box traveled 5 meters.
 
goonking said:
I'm not sure what you mean by fixed, but it is friction less.
I mean it can't move.

What direction, what distance, and with what acceleration does the block move?
 
Nathanael said:
I mean it can't move.

What direction, what distance, and with what acceleration does the block move?

the ramp is fixed.
the box goes up the ramp.

the distance it travels before flying off the ramp is 5 meters.

and I have no idea how to calculate the acceleration. I assume it slows down near the top since it is going against gravity.
 
goonking said:
the ramp is fixed.
the box goes up the ramp.

the distance it travels before flying off the ramp is 5 meters.

and I have no idea how to calculate the acceleration. I assume it slows down near the top since it is going against gravity.
It slows down the whole way. But at what rate?

Have you tried drawing a free body diagram? What are all the forces acting on the block?
 
Nathanael said:
It slows down the whole way. But at what rate?

Have you tried drawing a free body diagram? What are all the forces acting on the block?
Since it's frictionless, the only forces are gravity and normal force. correct? also the force from the initial push
 
goonking said:
Since it's frictionless, the only forces are gravity and normal force. correct? also the force from the initial push
Right, but the force from the initial push is irrelevant. We can "start our clocks" immediately after that force stops; when the block is moving at 12 m/s

What is the size and direction of the normal force? And what is the net force that results from adding gravity and the normal force together?
 
Nathanael said:
Right, but the force from the initial push is irrelevant. We can "start our clocks" immediately after that force stops; when the block is moving at 12 m/s

What is the size and direction of the normal force? And what is the net force that results from adding gravity and the normal force together?
direction of normal force is perpendicular to the surface.
the size of the normal force is... http://imgur.com/UOZntLH , the red line, correct?
 
  • #10
Yes but it's time to get into equations: What is the size of the normal force? More importantly, what is the size of the net force?
 
  • #11
Nathanael said:
Yes but it's time to get into equations: What is the size of the normal force? More importantly, what is the size of the net force?
I edited out my posit made no sense, to have Fg, we need the mass of the object, and that isn't given.
 
  • #12
Nathanael said:
Yes but it's time to get into equations: What is the size of the normal force? More importantly, what is the size of the net force?
but it should be cos theta = Fg⊥ to surface divided by Fg. correct?
 
  • #13
goonking said:
to have Fg, we need the mass of the object, and that isn't given.
Maybe all hope is not lost, just continue as normal. The mass is hereby an arbitrary "m"

goonking said:
but it should be cos theta = Fg⊥ to surface divided by Fg. correct?
Right, so that gives you |F| = |Fg|cosθ

So what is the sum of the two vectors F+Fg ?
 
  • #14
Nathanael said:
Maybe all hope is not lost, just continue as normal. The mass is hereby an arbitrary "m"Right, so that gives you |F| = |Fg|cosθ

So what is the sum of the two vectors F+Fg ?
|F⊥| = |Fg|cosθ= 7.84

Fg = 9.8

so adding them is 9.8 + 7.84 = 17.64

is that correct?
 
  • #15
goonking said:
|F⊥| = |Fg|cosθ= 7.84

Fg = 9.8

so adding them is 9.8 + 7.84 = 17.64

is that correct?
No, these are vectors. They have directions. You must add them component by component. Consider the component of gravity perpendicular to the ramp... How does it combine with the normal force? What net force do they produce in the direction perpendicular to the ramp? Then what is left of gravity?
 

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