What is the correct acceleration for the inclined pulley problem?

In summary: You have two masses, so two FBDs, and 2 unknowns ( the tensions ).In summary, the conversation discusses the masses and coefficients of friction of two objects, m1 and m2, on an inclined plane. The question is whether the masses will start to move if released, and how much additional mass is needed to cause them to move. The acceleration of the masses is also discussed, with the expected answer being 5.7 m/s2, achievable through solving for the tensions in the free body diagrams of the two masses.
  • #1
Coco12
272
0

Homework Statement

m1 has a mass of 47 kg and m2 has a mass of 35 kg. the coefficient of friction between m1 and the surface of the inclined plane are us=.42 and uk=.19 m1 is on an inclined plane angled 25 degrees

A) if the masses are held in place and then released, will they start to move?
B) what mass would you have to add to m2 to cause the masses to begin to move?
C) what would be the acceleration of the masses after adding the additional mass?

Homework Equations


For a- I know the answer is no
For b- made fnet equal to 0 and solved for m2. (37.8) subtracted 37.8 from 35 to get 2.8kg of additional mass

The Attempt at a Solution


For c- I used fnet=ma fnet= -Ff-fparallel+m2g/m1+m2
However I didn't get the right answer which is supposed to be 5.7 m/s2 ..
What am I doing wrong??
 
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  • #2
It's not clear what is going on. How are two masses connected ( if they are ), and where is m2 ?
 
  • #3
M2 is suspended in the air m1 is on an incline, connected together by a pulley
 
  • #4
Could be a typo in the question. Suppose for a moment that all surfaces were without friction. What would the acceleration be then? Is your expected "right answer" achievable?
 
  • #5
I have no idea how they got tht answer.. How would you go about solving that?
 
  • #6
Start with the free body diagrams, of course.
 

1. What is an inclined pulley problem?

An inclined pulley problem is a physics problem that involves a pulley system at an angle, usually with one or more masses attached to it. The goal of the problem is to find the acceleration of the masses and the tension in the rope.

2. How do I solve an inclined pulley problem?

To solve an inclined pulley problem, you will need to apply Newton's laws of motion and the principles of mechanical advantage. Draw a free-body diagram and break down the forces acting on the masses. Then, use trigonometry to resolve the forces into horizontal and vertical components.

3. What are the key equations for solving an inclined pulley problem?

The key equations for solving an inclined pulley problem are Newton's second law, which states that the net force on an object is equal to its mass multiplied by its acceleration (F=ma), and the principle of mechanical advantage, which states that the force exerted by the rope is equal to the tension in the rope multiplied by the mechanical advantage of the pulley system.

4. What are the common mistakes when solving an inclined pulley problem?

One common mistake is not taking into account the mass of the pulley itself. Another mistake is not properly resolving the forces into horizontal and vertical components. It is also important to ensure that the direction of the acceleration is consistent with the direction of the net force.

5. Are there any shortcuts for solving an inclined pulley problem?

While there are no shortcuts for solving an inclined pulley problem, it can be helpful to use the principle of mechanical advantage to simplify the equations and reduce the number of unknown variables. It is also important to check your answer using multiple methods, such as using energy conservation or checking for equilibrium.

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