Solving Velocity of a Box Off a Ramp

[goonking]

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?

 

[Nathanael]

The ramp is fixed and frictionless, right?

a is gravity so it is -9.8, correct?

Is gravity the only force acting on the box? In which direction is it accelerating?

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?

 

[goonking]

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.

 

[Nathanael]

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?

 

[goonking]

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.

 

[Nathanael]

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?

 

[goonking]

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

 

[Nathanael]

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?

 

[goonking]

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?

 

[Nathanael]

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?

 

[goonking]

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.

 

[goonking]

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?

 

[Nathanael]

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"

but it should be cos theta = Fg⊥ to surface divided by Fg. correct?

Right, so that gives you |F_⊥| = |F_g|cosθ

So what is the sum of the two vectors F_⊥+F_g ?

 

[goonking]

Maybe all hope is not lost, just continue as normal. The mass is hereby an arbitrary "m"Right, so that gives you |F_⊥| = |F_g|cosθ

So what is the sum of the two vectors F_⊥+F_g ?

|F⊥| = |Fg|cosθ= 7.84

Fg = 9.8

so adding them is 9.8 + 7.84 = 17.64

is that correct?

 

[Nathanael]

|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?