Inclined plane with friction, find kinetic energy.

In summary, the conversation discusses a physics problem involving two blocks attached to a rope on an inclined plane. The angle of the plane and the coefficient of kinetic friction are given, and the goal is to find the variation of kinetic energy as one of the blocks moves up 20 meters. The conversation includes a solution attempt, with a few minor typos corrected, and concludes with gratitude for the help provided.
  • #1
dttah
37
0
I need someone to double check it, because this was an exam given by my teacher and I am trying to solve it, but I do not have any results so I would like to know if I did it correctly or not. Thank you!

Homework Statement



Two blocks m1 = 50kg and m2= 100kg are attached to a rope as shown in figure. Pulley is massless. The angle of the inclined plane is pi/6 and the coefficient of kinetic friction is 0.250. Find the variation of kinetic energy if the body m1 goes up 20meters.

Homework Equations


F = ma
kinetic energy = 1/2 mv^2
kinetic friction = mu*normal force.

The Attempt at a Solution


See attachment
or: http://i40.tinypic.com/6hklm8.jpg for better quality.

Thanks for any help.
 

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  • #2
Welcome to PF! Thanks for taking time to show your whole solution so clearly.

Over on the right side, where you first have "a =", it appears you are missing a "-m₂g" in the numerator. Also, the "μ*m₁*cos(30)" should have a factor of g as well. I end up with a negative acceleration (m₂ goes down) of about 4.
 
  • #3
Aw, how could I fall in such a stupid typos mistakes ! :(.
Thanks a lot, that's appreciated. Forgetting about the "numbers" is the reasoning correct ( I mean the use of the formulas) or is there anything wrong? Thanks a lot!
 
  • #4
Yes, it all looks good! Nice use of variables right up to the calculation stage.
 
  • #5
Alright! Thanks a lot, I am grateful and I appreciate your help. Thanks again :)
 
  • #6
Most welcome.
 

1. What is an inclined plane with friction?

An inclined plane with friction is a simple machine that consists of a flat surface that is tilted at an angle, with a rough surface to create friction. It is used to reduce the force needed to move an object up or down the plane.

2. How do you calculate the kinetic energy of an object on an inclined plane with friction?

The formula for calculating kinetic energy is 1/2 * mass * velocity^2. However, on an inclined plane with friction, the formula is adjusted to account for the work done against friction. It is given by KE = 1/2 * mass * (velocity^2 - 2 * friction * distance).

3. What factors affect the kinetic energy on an inclined plane with friction?

The factors that affect the kinetic energy on an inclined plane with friction are the mass of the object, the angle of the incline, the coefficient of friction, and the distance traveled. These factors influence the amount of work done against friction, which ultimately affects the kinetic energy of the object.

4. How does the coefficient of friction affect the kinetic energy on an inclined plane?

The coefficient of friction is a measure of the roughness of the surface and affects the amount of friction present on the inclined plane. A higher coefficient of friction will result in more work being done against friction, therefore reducing the kinetic energy of the object. On the other hand, a lower coefficient of friction will result in less work being done against friction, leading to a higher kinetic energy.

5. Can the kinetic energy on an inclined plane with friction be greater than the potential energy?

Yes, the kinetic energy on an inclined plane with friction can be greater than the potential energy. This is because some of the potential energy is converted into kinetic energy as the object moves down the inclined plane. However, the total mechanical energy (sum of kinetic and potential energy) will remain constant, as energy cannot be created or destroyed, only transferred or transformed.

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