cq_1_151

Phy 231

Your 'cq_1_15.1' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.

** **

A rubber band begins exerting a tension force when its length is 8 cm. As it is stretched to a length of 10 cm its tension increases with length, more or less steadily, until at the 10 cm length the tension is 3 Newtons.

• Between the 8 cm and 10 cm length, what are the minimum and maximum tensions?

answer/question/discussion: ->->->->->->->->->->->-> :

F = kx

3 = k*.1

That would be 3 N = k * .02 m, or 3 N = k * 2 cm.

k = 30

see above, and note that k has units

F = kx

F = 30*.08

F = 2.4

The max tension is given at 3N, the minimum tension is 2.4N.

• Assuming that the tension in the rubber band is 100% conservative (which is not actually the case) what is its elastic potential energy at the 10 cm length?

answer/question/discussion: ->->->->->->->->->->->-> :

If the system is conservative, the potential energy would be equal to the total work done. Calculating the total work, we get W = F*d = 3*10 = 30J. That means the elastic potential energy would be 30J at 10cm.

• If all this potential energy is transferred to the kinetic energy of an initially stationary 20 gram domino, what will be the velocity of the domino?

answer/question/discussion: ->->->->->->->->->->->-> :

K = 1/2 mv^2

30J = 1/2 * .02 v^2

30 = .01v^2

3000 = v^2

v = 54.77 m/s

• If instead the rubber band is used to 'shoot' the domino straight upward, then how high will it rise?

answer/question/discussion: ->->->->->->->->->->->-> :

F = ma

3 = .02*a

a = 150

U = mgh

30J = .02*150*h

30 = 3h

h = 10 m

** **

20 min

** **

I forgot that the Seed Question had its own submit page so I accidentally submitted it in the Submit Work Form as well.

You're applying the right formulas, but you're not being careful enough with your units.

I recommend that this be reasoned out at a lower level, closer to the definitions, then reconciled with the formulas.

&#Please compare your solutions with the expanded discussion at the link

Solution

Self-critique your solutions, if this is necessary, according to the usual criteria. Insert any revisions, questions, etc. into a copy of this posted document. Mark any insertions with &&&& so they can be easily identified. &#