# Three blocks, two pulleys, on a incline

• gap0063
In summary: Since m1=7.7 and is bigger than 2.29 the acceleration is pulling m3 up and m1 down... so the acceleration is 9.8 m/s2 for all three blocks.
gap0063

## Homework Statement

The suspended 2.29 kg mass on the right is
moving up, the 1.3 kg mass slides down the
ramp, and the suspended 7.7 kg mass on the
left is moving down. There is friction between
the block and the ramp.
The acceleration of gravity is 9.8 m/s2 . The
pulleys are massless and frictionless.
[PLAIN]http://img816.imageshack.us/img816/6190/009q.png

What is the acceleration of the three block
system?

## Homework Equations

The sum of Fx= N-mgcostheta=o => N=mgcostheta
The sum of Fy= mgsintheta-usN=0=> mgsintheta-us(mgcostheta)

## The Attempt at a Solution

are these the correct eqations for this?

Last edited by a moderator:
You'll want to look at each block in isolation. The system will have the same acceleration.

What forces act on the two hanging blocks?
What forces act on the block sliding down the incline?

What direction is the net acceleration?

Hint: there are two tension forces.

For the mass on the incline, choose the horizontal axis as the x axis, and the axis perpendicular to the incline as the y axis. In which case you have your Fx and Fy equations reversed. Then once corected , this will give you the normal force acting on that one block on the incline. That's step one...then its free body, free body, free body diagrams! Answer jhae2.718 questions. Look at each block separately, identify alll forces acting, and apply Newton's laws.

jhae2.718 said:
You'll want to look at each block in isolation. The system will have the same acceleration.

What forces act on the two hanging blocks?
What forces act on the block sliding down the incline?

What direction is the net acceleration?

Hint: there are two tension forces.

For block on the left... the mass I'll call m1... the forces acting on it are T1 acting up and m1g acting down

For block on incline... the mass I'll call m2... the forces act on it in the y direction of N and m2g and in the x directuon fk and T2

For the block on the right... the mass I'll call m3... the forces acting on it are T1 acting up and m3g acting down

Since m1=7.7 and is bigger than 2.29 the acceleration is pulling m3 up and m1 down...

So if I use the equations I gave before for the block on the incline and just use
sum of Fy=T1-mg=0 => T1=mg

but where does the acceleration come in for m1 and m3?

Yes, those equations are correct for this problem. In order to find the acceleration of the three block system, you will need to use Newton's second law, which states that the net force on an object is equal to its mass times its acceleration (F=ma). You will also need to consider the forces acting on each block individually. For example, for the 2.29 kg block on the right, the net force would be equal to the tension in the rope pulling it up minus the force of friction from the ramp. Once you have calculated the net force for each block, you can use Newton's second law to find the acceleration of the system.

## 1. What is the purpose of using three blocks and two pulleys on an incline?

The use of three blocks and two pulleys on an incline allows for an increased mechanical advantage, making it easier to lift heavier objects. This setup also allows for changes in direction of the force applied, making it useful for lifting objects up an incline.

## 2. How does the angle of the incline affect the system?

The angle of the incline affects the amount of resistance the system experiences. A steeper incline will result in a greater resistance, while a shallower incline will result in a lesser resistance. This is due to the influence of gravity on the objects being lifted.

## 3. What factors influence the amount of weight that can be lifted using this system?

The amount of weight that can be lifted using this system is influenced by the mechanical advantage of the pulleys, the angle of the incline, and the strength and stability of the materials used. Friction and other external forces may also play a role in the lifting capacity.

## 4. Can this system be used to lift objects at any angle of incline?

This system can be used to lift objects at various angles of incline, but the efficiency of the system may vary. In general, a shallower incline will result in a more efficient use of the system, while a steeper incline may require more force to lift the same weight.

## 5. Are there any safety precautions that should be taken when using this system?

It is important to properly secure and stabilize the system to prevent it from tipping or falling. Additionally, care should be taken to not overload the system, as this could result in damage or failure. Proper training and understanding of the system and its limitations is also recommended for safe use.

Replies
16
Views
4K
Replies
1
Views
1K
Replies
27
Views
6K
Replies
19
Views
3K
Replies
3
Views
1K
Replies
3
Views
1K
Replies
5
Views
2K
Replies
68
Views
10K
Replies
3
Views
2K
Replies
19
Views
2K