How Do You Calculate Tension in a Pulley System with Friction?

  • Thread starter howsockgothap
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In summary, the problem involves two blocks connected by a string and a frictionless, negligible mass pulley. The coefficient of kinetic friction between one of the blocks and an incline is given. The tension in the string, acceleration of the system, and decrease in total mechanical energy are to be determined. The tension can be found by setting up the blocks into vectors and using the equation Fnet=W-T. The decrease in energy can be calculated using the equation T=mg+fgsin37. The final answer should be 589 N.
  • #1
howsockgothap
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Homework Statement



Two blocks of mass m1=50.0 kg and m2=100 kg are connected by a string of negligible mass. The pulley is frictionless and also of negligible mass. The coefficient of kinetic friction between the 50.0 kg block and the incline is 0.250.

a) Determine the tension in the string.
b) Find the acceleration of the system.
c) Determine the decrease in total mechanical energy of the system (due to the presence of the frictional force) when the 50.0 kg block moves from point A to point B, a distance of 20.0 m.

Homework Equations



T=??

The Attempt at a Solution



I am fairly certain that I'll only need help with part a. I have a really hard time figuring out what to set tension equal to (and why). I had T-mg=F for the 100 kg block, but figured I couldn't do much with that. Instead I tried with the second block to use T=mg+fgsin37 but the answer I get is somewhere in the 3000s while my study guide says I should be getting 589 N. How do I go about setting up tension for this problem?
 

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  • #2
try setting up the blocks into vectors first, this may help you be able to realize what you can set equal to one another
 
  • #3
then u should consider Fnet=W-T after you determine your vectors
 
  • #4
I'm not quite sure what you mean by Fnet=W-T

I don't see how work comes into this system, since it seems to me that I don't have any 'initial' conditions from which to determine energy.
 
Last edited:
  • #5
NVM got it. Thanks!
 

1. What is a tension/pulley problem?

A tension/pulley problem is a type of physics problem that involves calculating the tension force in a rope or cable connected to one or more pulleys. These problems typically involve multiple masses connected by ropes or cables passing over pulleys, and require the use of Newton's laws of motion and principles of equilibrium to solve.

2. What are the key concepts involved in solving a tension/pulley problem?

The key concepts involved in solving a tension/pulley problem include Newton's laws of motion, specifically the laws of inertia, acceleration, and action-reaction; and the principle of equilibrium, which states that the net force and net torque on an object must be equal to zero for it to be in a state of equilibrium.

3. How do you approach solving a tension/pulley problem?

The first step in solving a tension/pulley problem is to identify all the forces acting on the system, including the weight of the masses, the tension in the ropes, and any external forces. Next, apply Newton's laws of motion and the principle of equilibrium to set up a system of equations. Finally, solve for the unknown variables using algebraic manipulation.

4. What are some common mistakes to avoid when solving a tension/pulley problem?

Common mistakes when solving a tension/pulley problem include forgetting to include all the forces acting on the system, using incorrect signs for forces or angles, and not properly setting up the equations of motion. It is also important to double-check units and make sure they are consistent throughout the calculations.

5. Are there any tips or tricks for solving tension/pulley problems?

Some tips for solving tension/pulley problems include drawing a clear diagram of the system, labeling all the forces and angles, and using trigonometric functions to break forces into their horizontal and vertical components. It can also be helpful to approach the problem from different angles and try different methods of solving to find the most efficient solution.

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