Physics question on Energy and Spring, any help appreciated

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Homework Help Overview

The discussion revolves around a physics problem involving energy conservation and spring mechanics. The original poster presents a scenario where a puck compresses a spring after sliding on frictionless ice, with two parts to the question: one without friction and one with a frictional force acting on the puck.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to apply energy conservation principles to determine the maximum compression of the spring in both scenarios. There is uncertainty regarding the role of friction in the second part of the problem, particularly concerning the value of Δd.

Discussion Status

Participants are engaging in clarifying the relationship between the compression of the spring and the distance over which friction acts. Some guidance has been offered regarding the definitions of variables and the application of energy equations, but no consensus has been reached on the final approach to the problem.

Contextual Notes

There is a noted confusion about the definitions of Δd and x, particularly in relation to the transition from part a to part b of the problem. The discussion reflects the challenges of integrating friction into the energy conservation framework.

DiaperBoy35
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Physics question on Energy and Spring, any help appreciated :D

Homework Statement



a. A 1.0 kg puck sliding at 15 m/s along some horizontal frictionless ice strikes and compresses a horizontal spring attached to one end of the ice rink. If the spring has a constant of 35 N/m, what is the maximum compression of the spring?

b. If in the above problem, the puck experiences a constant frictional force of 4.0 N opposing its motion beginning when it first strikes the spring, what would the maximum compression of the spring now be? (10 marks)


I am unsure about part b, as i am not sure what to use for the value of Δd as you will see underneath at my attempt

Homework Equations



-0.5mv^2 (1) + 0.5kv^2 (1)= 0.5mv^2 (1) + 0.5kv^2 (1)

- E(thermal) = Frictional force x Δd

The Attempt at a Solution



E(total 1) = E (total 2)
0.5mv^2 (1) + 0.5kv^2 (1)= 0.5mv^2 (1) + 0.5kv^2 (1) [ 0.5kv^2 (1) and 0.5mv^2 (1) equal 0]
0.5mv^2 (1) = 0.5kv^2 (1)
x = √((15^2)/35)
x = 2.535 m


[ (1) <-- denotes to initial (2)<-- denotes to final]

Part b
E(total 1) = E (total 2)
0.5mv^2 (1) + 0.5kv^2 (1)= 0.5mv^2 (1) + 0.5kv^2 (1) + E(thermal) [ 0.5kv^2 (1) and 0.5mv^2 (1) equal 0]
0.5mv^2 (1) = + 0.5kv^2 (1) + Ff Δ d

I am unsure of what to do from here

[ (1) <-- denotes to initial (2)<-- denotes to final]
 
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The amount by which the spring compresses, x, is the same as the distance over which work is done by friction, which you have called Δd.

Oh, and by the way, the elastic potential energy is given by (1/2)kx2. (It should be an x, not a v).
 


Oh yes, i meant kx :P
thank you for that

But why would Δd be the x value from part a?
 


DiaperBoy35 said:
Oh yes, i meant kx :P
thank you for that

But why would Δd be the x value from part a?

Δd is not the x value from part a. Δd is the x value from part b! :-p

The reason is because the frictional force starts up at the instant that the object touches the spring. So the distance over which the spring is compressed (before the thing comes to a stop) is the same as the distance over which the friction acts.
 


Ohhhhhh Thank youu so much!
I was really confused with that question lol
 

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