Solving Heat Energy Dissipation for a Falling Magnet

[carpelumen]

Homework Statement

A magnet of mass 0.10 kg is dropped from rest and falls vertically through a 35.0 cm copper tube. Eddy currents are induced, causing the copper to warm up. The speed of the magnet as it emerges from the tube is 1.50 m/s. How much heat energy is dissipated to the environment?

Homework Equations

E = mgh

The Attempt at a Solution

h = 35 cm --> .35 m

E = (.10 kg) * (9.81) * (.35 m) = .3433 J

Is the equation incorrect?

 

[ehild]

Homework Statement

A magnet of mass 0.10 kg is dropped from rest and falls vertically through a 35.0 cm copper tube. Eddy currents are induced, causing the copper to warm up. The speed of the magnet as it emerges from the tube is 1.50 m/s. How much heat energy is dissipated to the environment?

Homework Equations

E = mgh

The Attempt at a Solution

h = 35 cm --> .35 m

E = (.10 kg) * (9.81) * (.35 m) = .3433 J

Is the equation incorrect?

It is the initial energy if you take the potential energy zero at the bottom of the tube. But what is the loss of energy?

ehild

 

[NascentOxygen]

Homework Statement

A magnet of mass 0.10 kg is dropped from rest and falls vertically through a 35.0 cm copper tube. Eddy currents are induced, causing the copper to warm up. The speed of the magnet as it emerges from the tube is 1.50 m/s. How much heat energy is dissipated to the environment?

Homework Equations

E = mgh

The Attempt at a Solution

h = 35 cm --> .35 m

E = (.10 kg) * (9.81) * (.35 m) = .3433 J

Is the equation incorrect?

What happens to the P.E. that you have just calculated the magnet loses?

 

[Jakob Weg]

An illustrative experiment on this issue

 

[rude man]

An illustrative experiment on this issue

Good! We note that a larger-diameter tube slows the magnet down more than a smaller-diameter one, following emf = -dΦ/dt. Also that Cu slowed the magnet down more than did Al or brass, following i = emf/R. Vielen Dank!

 

[rude man]

Homework Statement

A magnet of mass 0.10 kg is dropped from rest and falls vertically through a 35.0 cm copper tube. Eddy currents are induced, causing the copper to warm up. The speed of the magnet as it emerges from the tube is 1.50 m/s. How much heat energy is dissipated to the environment?

Homework Equations

E = mgh

The Attempt at a Solution

h = 35 cm --> .35 m

E = (.10 kg) * (9.81) * (.35 m) = .3433 J

Is the equation incorrect?

That's the kinetic energy (k.e.) that would have developed in the absence of the copper tube. What was the k.e. with the tube?