Solving Torque on a Pulley: 0.5Nm, 4kg Block, 12cm Diameter

In summary, the problem involves two blocks connected by a massless rope over a pulley with a mass of 2kg and a diameter of 12cm. The friction at the pulley's axle exerts a torque of 0.5Nm. Given that the blocks are released from rest, the question is how long it takes for the 4kg block to reach the floor. The approach involves calculating the total torque, finding the angular acceleration, and solving for the tangential acceleration. However, the answer may differ from other sources due to the tension in the ropes being the source of torque, not the weights of the hanging blocks. Additional equations may be needed to solve for the acceleration.
  • #1
cjavier
17
0
The problem is: The two blocks in the figure are connected by a massless rope that passes over a pulley. The pulley is 12cm in diameter and has a mass of 2kg. As the pulley turns, friction at the axle exerts a torque of magnitude 0.5Nm. If the blocks are released from rest, how long does it take the 4 kg block to reach the floor?
Here is the picture:
pulley3.png


My approach was as follows:
Ʃτ = τleft-weight - τtension - τright-weight
Then, when I found total torque...
Ʃτ = I[itex]\alpha[/itex]([itex]\alpha[/itex] is angular acceleration)
Then finally...
atangential = [itex]\alpha[/itex]r

When I found a, however, it was different than the answer on chegg. What am I doing wrong?

Thanks To Everyone on this site
 
Physics news on Phys.org
  • #2
cjavier said:
My approach was as follows:
Ʃτ = τleft-weight - τtension - τright-weight
What exerts the torque on the pulley is the tension in the ropes, not the weights of the hanging.

Of course, those tensions depend on the weights. You'll need additional equations for each mass to solve for the acceleration.
 

FAQ: Solving Torque on a Pulley: 0.5Nm, 4kg Block, 12cm Diameter

1. How do you calculate the torque on a pulley?

To calculate torque on a pulley, you need to know the force being applied (in newtons) and the distance between the force and the axis of rotation (in meters). The formula for torque is torque = force x distance.

2. What is the unit of measurement for torque?

The unit of measurement for torque is newton-meters (Nm). This is a combination of the unit for force (newtons) and the unit for distance (meters).

3. How does the diameter of the pulley affect the torque?

The diameter of the pulley affects the torque by changing the distance between the force and the axis of rotation. The larger the diameter, the larger the distance, resulting in a greater torque.

4. Can you have negative torque on a pulley?

Yes, torque can be negative on a pulley if the direction of the force is opposite to the direction of rotation. This can happen if, for example, the pulley is being used to lift a weight and then the weight is lowered back down.

5. How can you increase the torque on a pulley?

To increase the torque on a pulley, you can either increase the force being applied or increase the distance between the force and the axis of rotation. You can also use a larger diameter pulley, which will increase the distance and therefore the torque.

Similar threads

Analyzing acceleration of block on a ramp connected to a pulley
Replies
15
Views
570
Blocks falling while attatched to pulley
Replies
6
Views
2K
Angular acceleration of an atwood pulley
Replies
8
Views
3K
Defining equilibrium and movement in pulley arrangements
Replies
8
Views
2K
Experimental Design: Pulley and Mass Hangers
Replies
30
Views
2K
Force applied on the pulley of a system
Replies
8
Views
2K
Net torque question? Block 1 and block 2 hanging on pulley?
Replies
2
Views
5K
Torque of Pulley with Two Masses2
Replies
6
Views
1K
What are the accelerations of the blocks?
Replies
5
Views
1K
Explain friction in a pulley system
Replies
13
Views
6K

Hot Threads

Recent Insights

Back
Top