Two blocks with pulley, friction

In summary, the question asks for the acceleration of two blocks, with masses 8.2 kg and 25 kg, connected by a pulley with mass 5.9 kg and radius 0.25 m. The pulley is assumed to be frictionless, but there is a coefficient of friction between the blocks and the surface. The acceleration of the 25 kg block is given as a, and the moment of inertia of the pulley is 1/2MR^2. The acceleration of gravity is 9.8 m/s^2. The equations used to solve the problem are torque= (radius)(force)sin(angle between them)= (
  • #1
nazerofsun
7
0

Homework Statement


Consider the setup shown below. The blocks
have masses 8.2 kg and 25 kg. The pulley
has mass 5.9 kg, and is a uniform disc with
radius 0.25 m. Assume the pulley to be fric-
tionless, but the coefficient of friction between
the block and the surface is 0.28.What is the
acceleration of the blocks? Assume the 25 kg
mass is descending with acceleration a. The
moment of inertia of the disk is 1/2MR2 and the
acceleration of gravity is 9.8 m/s2 .
Answer in units of m/s2.


Homework Equations


Torque= (radius)(force)sin(angle between them)= (inerta)*(alpha)or (inertia)*a/r
sumF=ma
friction= (mew)*(normal force)

The Attempt at a Solution


mo= mass of pulley

I think this problem just has too much algebra =.=
sumF1x= m1gsin(theta)+Friction-T1=m1a
SumF2y=T2-m2g=m2a
sumT= 1/2(mo)ra= rt1-rt2 ( I don't know which one should go first or why)
solving the t and plugging it into torque I receive:

a= g( (1+(mew))m1sin(theta)-m2)
-----------------------------
(1/2mo+m1+m2)

I have a practice problem I can use to verify if i set this problem up but I keep getting like .05 off -.-

Any help would be appreciated!
 
Last edited:
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  • #2
Show a picture of the set-up and show your work.

ehild
 

1. How does friction affect the movement of two blocks with a pulley?

Friction is a force that opposes the relative motion between two surfaces in contact. In the case of two blocks with a pulley, friction can act in the direction of motion, slowing down the blocks, or in the opposite direction, helping to maintain their position.

2. What role does the pulley play in the system of two blocks?

The pulley is a simple machine that helps to change the direction of the force applied. In the system of two blocks, the pulley helps to distribute the force of gravity evenly between the two blocks, allowing for a more balanced and efficient movement.

3. How does the weight of the blocks affect the tension in the rope?

The tension in the rope is directly proportional to the weight of the blocks. As the weight of the blocks increases, the tension in the rope also increases, and vice versa.

4. What is the formula for calculating the acceleration of the two blocks in this system?

The formula for calculating the acceleration of the two blocks is a = (m1-m2)/(m1+m2+mu), where m1 and m2 are the masses of the two blocks and mu is the coefficient of friction between the blocks and the surface they are on.

5. Can the direction of the movement of the two blocks be reversed by changing the position of the pulley?

Yes, the direction of the movement of the two blocks can be reversed by changing the position of the pulley. By changing the angle of the rope over the pulley, the direction of the force applied to the blocks can be reversed, causing them to move in the opposite direction.

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