Spring, Friction, Incline, Mass moving up a Ramp

In summary, the angle of incline affects the speed of a mass moving up a ramp by increasing the gravitational force pulling the mass down. Friction acts against the movement of the mass, slowing it down, and the weight of the mass also plays a role in the force needed to move it up the ramp. The spring force counteracts the force of gravity, helping the mass move up the ramp with less resistance. However, the speed of the mass cannot be calculated using the spring force alone, as it depends on a combination of forces including gravity, friction, and the force of the spring.
  • #1
twilos
13
0

Homework Statement


A 2.1 kg is released from rest from the bottom of a 45 degree inclined ramp. The package is attached to an ideal spring K = 35 N/m that is attached to the top of the incline causing the package to be launched up the incline. The coefficients of friction between the package and the surface are Us = 0.35 and Uk = 0.25

When the package is released, the spring is elongated 1.3m from its equilibrium position just before going up the ramp.

A. What is the speed of the package when the spring reaches its equilibrium position on the way up?

B. What will be the maximum compress of the spring?

Homework Equations



Kf + Ui = Ki + Ui + Other forces

Fs = 1/2kx^2

Ug = mg(sin45)

Us = 1/2kx^2

The Attempt at a Solution



I been trying to figure out how to set up the problem because i am unsure where Uspring and Ugravity are replacing in the conservation of energy. But here i go:

Kf + Ui = Ki + Ui + Other forces

1/2mv^2 + mg(sin45) = 0 + 1/2kx^2 - fkD

(.5)(2.1kg)(v^2) + (2.1kg)(9.8 m/s^2)(sin 45) = (.5)(35 N/m)(1.3m)^2 - (0.25)(2.1kg)(9.8 m/2^2)(cos45)(1.3)

also once you get the vf from part A you can find Part B's maximum compress which is K by using conservation of energy and substituting vf in and solving for K correct?
 
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  • #2
for Part B where you find the maximum compress I believe i am wrong and your actually finding X which is the distance the spring is compressed. Therefore when you find Vf you substitute it back into the conservation of energy equation and solve for X or D which i used both. And there will probably be some quadractic equation?
 
  • #3
twilos said:

Homework Statement


A 2.1 kg is released from rest from the bottom of a 45 degree inclined ramp. The package is attached to an ideal spring K = 35 N/m that is attached to the top of the incline causing the package to be launched up the incline. The coefficients of friction between the package and the surface are Us = 0.35 and Uk = 0.25

When the package is released, the spring is elongated 1.3m from its equilibrium position just before going up the ramp.

A. What is the speed of the package when the spring reaches its equilibrium position on the way up?

B. What will be the maximum compress of the spring?

Homework Equations



Kf + Ui = Ki + Ui + Other forces

Fs = 1/2kx^2

Ug = mg(sin45)

Us = 1/2kx^2

The Attempt at a Solution



I been trying to figure out how to set up the problem because i am unsure where Uspring and Ugravity are replacing in the conservation of energy. But here i go:

Kf + Ui = Ki + Ui + Other forces

1/2mv^2 + mg(sin45) = 0 + 1/2kx^2 - fkD

(.5)(2.1kg)(v^2) + (2.1kg)(9.8 m/s^2)(sin 45) = (.5)(35 N/m)(1.3m)^2 - (0.25)(2.1kg)(9.8 m/2^2)(cos45)(1.3)

also once you get the vf from part A you can find Part B's maximum compress which is K by using conservation of energy and substituting vf in and solving for K correct?
Welcome to PF.

Basically you are correct. Once you have the kinetic energy at the point that the spring is exerting no more force - changes from stretching to compression - then you use that kinetic energy to determine how much potential energy you can purchase and how much more friction will steal.
 
  • #4
LowlyPion said:
Welcome to PF.

Basically you are correct. Once you have the kinetic energy at the point that the spring is exerting no more force - changes from stretching to compression - then you use that kinetic energy to determine how much potential energy you can purchase and how much more friction will steal.

Just to clarify, that was all for part A right? Now to find the max compression of the spring do i keep all the variables still i.e kinetic, potential gravitational, potential spring, friction? And do i solve for k or x/D?
 
  • #5
twilos said:
Just to clarify, that was all for part A right? Now to find the max compression of the spring do i keep all the variables still i.e kinetic, potential gravitational, potential spring, friction? And do i solve for k or x/D?

I was referring to part B.

In A you have the PE of the spring being spent up until equilibrium on the PE increase, the KE increase and the expense of friction.

In B then it's the KE going back into Spring PE and gravity PE and the expense of friction.

As to solving, then of course it's x that you solve for since k is the same either way for the ideal spring.
 
  • #6
Awesome i actually understood the concept now... =) so we're splitting Part A into the Before and Part B into the After. And Part B will be looked at again with the conservation of energy as "the KE going back into Spring PE and gravity PE and the expense of friction." correct?
 
  • #7
twilos said:
Awesome i actually understood the concept now... =) so we're splitting Part A into the Before and Part B into the After. And Part B will be looked at again with the conservation of energy as "the KE going back into Spring PE and gravity PE and the expense of friction." correct?

That's the idea.
 

1. How does the angle of incline affect the speed of a mass moving up a ramp?

The steeper the incline, the faster the mass will move up the ramp. This is because the component of the gravitational force pulling the mass down the ramp increases as the angle of incline increases.

2. How does friction affect the movement of a mass up a ramp?

Friction acts in the opposite direction of the movement of the mass, slowing it down. The amount of friction depends on the type of surface the ramp is made of and the weight of the mass.

3. How does the mass of the object affect its motion up a ramp?

A heavier mass will require more force to move up the ramp compared to a lighter mass. This is because the weight of the mass adds to the force of gravity pulling it down the ramp.

4. What is the role of spring force in this scenario?

The spring force acts in the opposite direction of the movement of the mass, counteracting the force of gravity pulling it down the ramp. This helps the mass move up the ramp with less resistance.

5. Can the speed of the mass moving up the ramp be calculated using the spring force?

No, the speed of the mass cannot be calculated using the spring force alone. The speed of the mass depends on the combination of forces acting on it, including gravity, friction, and the force of the spring.

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