Calculating Work and Change in Thermal Energy

[alyssad]

Homework Statement

In the question, a person is pulling a 156 kg sled up a hill. A 620 N force is used to pull the sled up the hill that has an angle of 29° with the horizontal. The sled is pulled a distance of 26 m, and the kinetic friction coefficient is 0.0622. The system has been defined as the sled and the surface of the ground.

I need to calculate the amount of work the person is using to pull the sled, and I need to calculate the change in the thermal energy experienced by the system.

Homework Equations

W = F*d*cos(Θ)
ΔE_th = F_kΔr

The Attempt at a Solution

I've been trying to do W = μ_kmgΔr*cos(Θ), but I don't think I'm doing it correctly.

And I think I need to know the work to make finding the change in thermal energy easier.

Thank you!

 

[SammyS]

Homework Statement

In the question, a person is pulling a 156 kg sled up a hill. A 620 N force is used to pull the sled up the hill that has an angle of 29° with the horizontal. The sled is pulled a distance of 26 m, and the kinetic friction coefficient is 0.0622. The system has been defined as the sled and the surface of the ground.

I need to calculate the amount of work the person is using to pull the sled, and I need to calculate the change in the thermal energy experienced by the system.

Homework Equations

W = F*d*cos(Θ)
ΔE_th = F_kΔr

The Attempt at a Solution

I've been trying to do W = μ_kmgΔr*cos(Θ), but I don't think I'm doing it correctly.

And I think I need to know the work to make finding the change in thermal energy easier.

Thank you!

It looks as though you have only found the work done by the person to overcome friction.

What if the coefficient of friction were zero. If so, would it not be the case that the person would still have to do work?

 

[Chestermiller]

The change in thermal energy is equal to the frictional work, assuming that the system consists of the universe.