Solving for Velocity on a Pulley System

In summary: You already have a=-b.Next, look at pulley C. What equation can you write for that? Then move on to pulley B.In summary, when solving a homework equation, Velocity on a pulley is (velocity on left rope + velocity right rope)/2. The equation for pulley C is: -vBR. Pulley B has an equation of: vB = (150+vBR)/2.
  • #1
RoyalFlush100
56
2

Homework Statement


In the picture below.

Homework Equations


Velocity on a pulley = (velocity on left rope + velocity right rope)/2
Pulley A and C have 0 velocity.

The Attempt at a Solution


By inspection the right sided rope on pulley A is 120 mm/s going up.
After that is when I get confused. Pulley B and D are in motion, so I don't see what else to do from here.
 

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  • #2
RoyalFlush100 said:
left sided rope on pulley A is 120 mm/s going up.
Looks like down to me.
RoyalFlush100 said:
Velocity on a pulley = (velocity on left rope + velocity right rope)/2
So apply that to each pulley in turn, working from the left.
What does it tell you about the velocity of the second rope segment (the one on the right of pulley A)?
 
  • #3
haruspex said:
Looks like down to me.

So apply that to each pulley in turn, working from the left.
What does it tell you about the velocity of the second rope segment (the one on the right of pulley A)?

Yeah, I meant the rope to the right.

But still, we don't know vB, meaning we'd have:
vB = (150+vBR)/2
Where vBR is the velocity on the right of pulley B.
By inspection vCL = -vBR

But from here, I'm not sure how to proceed since vB is not 0
 
  • #4
RoyalFlush100 said:
Yeah, I meant the rope to the right.
Ok.
I feel your notation is going to get a bit confusing since you will have two names for the same rope.
I'll just label them and their velocities a to e across the top, and the segment left of the lowest pulley is f.
You already have a=-b.
Next, look at pulley C. What equation can you write for that? Then move on to pulley B.
You don't need to solve these equations, determining velocities, as you go along. Just get all the equations written first.
 

FAQ: Solving for Velocity on a Pulley System

What is a pulley system?

A pulley system is a simple machine that consists of a wheel with a groove and a rope or chain wrapped around it. It is used to change the direction of a force and make it easier to lift or move heavy objects.

How do you calculate velocity on a pulley system?

To calculate velocity on a pulley system, you need to know the distance the object moves and the time it takes to move that distance. Then, you can use the formula velocity = distance/time to determine the velocity.

What is the difference between linear velocity and angular velocity on a pulley system?

Linear velocity is the speed at which an object moves in a straight line, while angular velocity is the speed at which an object rotates around a fixed point. In a pulley system, linear velocity refers to the speed at which the object being lifted moves up or down, while the angular velocity refers to the speed at which the pulley rotates.

How do you account for friction in calculating velocity on a pulley system?

Friction is a force that opposes motion and can affect the velocity on a pulley system. To account for friction, you can subtract the force of friction from the total force being applied to the object. This will give you a more accurate calculation of the object's velocity.

Can you increase the velocity on a pulley system?

Yes, the velocity on a pulley system can be increased by either increasing the force being applied to the object or by reducing the amount of friction in the system. However, there may be limitations based on the weight of the object and the strength of the pulley system.

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