Energy loss in a pulley, but cleverer

In summary, a block of mass 7.00×10-1kg is suspended by a string wrapped around a pulley with a radius of 5.80×10-2m. The moment of inertia of the pulley is 4.00×10-3kg*m2 and there is friction as it turns. Starting from rest, the block travels downwards a distance of 0.830m with a final speed of 1.611m/s. The goal is to calculate the amount of energy dissipated up to that point. Using the equations mgh=U(x), 1/2Iw^2, and I/2mv^2, the calculation for the energy lost is -3.25
  • #1
helloxkitty
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Homework Statement



A block of mass 7.00×10-1kg is suspended by a string which is wrapped so that it is at a radius of 5.80×10-2m from the center of a pulley. The moment of inertia of the pulley is 4.00×10-3kg*m2. There is friction as the pulley turns. The block starts from rest, and its speed after it has traveled downwards a distance of D=0.830m is 1.611m/s. Calculate the amount of energy dissipated up to that point.

given m, r, I, v, D, find Q (energy lost)

Homework Equations



mgh=U(x)
1/2Iw^2
I/2mv^2


The Attempt at a Solution



-mgh=1/2Iw^2+1/2mv^2+Q
solve for Q, get 8.15 J lost. I'm not really sure why I'm unable to get the right answer...unless 8.15 is supposed to be negative. Any thoughts? Thanks so much =)!
 
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  • #2
Hmm, your method is correct. I got -3.25 as the work done by friction. Show a bit more in depth how exactly you made your calculation.
 

Related to Energy loss in a pulley, but cleverer

What is energy loss in a pulley?

Energy loss in a pulley refers to the amount of energy that is lost during the transfer of energy from one system to another through the use of a pulley system. This energy loss can occur due to friction, mechanical inefficiencies, or other factors.

How does friction affect energy loss in a pulley?

Friction plays a significant role in energy loss in a pulley. When a pulley is used to transfer energy, the movement of the rope or belt over the pulley's surface creates friction, which can cause energy to be lost in the form of heat. This energy loss can be reduced by using materials with lower coefficients of friction or by lubricating the pulley's surface.

What are some factors that can increase energy loss in a pulley?

Aside from friction, there are other factors that can contribute to energy loss in a pulley. These include the weight and stiffness of the rope or belt, the type of pulley used, and the overall design and efficiency of the pulley system. Additionally, external factors such as temperature and humidity can also affect energy loss in a pulley.

How can energy loss in a pulley be minimized?

To minimize energy loss in a pulley, several steps can be taken. Using high-quality, low-friction materials for the pulley and the rope or belt can help reduce friction and energy loss. Proper maintenance and lubrication of the pulley system can also help to minimize energy loss. Additionally, using a well-designed and efficient pulley system can also help to reduce energy loss.

Why is it important to reduce energy loss in a pulley?

Reducing energy loss in a pulley is important because it can impact the overall efficiency and effectiveness of the system. The more energy that is lost, the less energy is available for the intended task. This can result in additional energy usage and increased costs. Minimizing energy loss in a pulley can also increase the lifespan of the system and reduce the need for frequent repairs or replacements.

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