Did i do this problem right? (Work by Spring and KE)

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Homework Help Overview

The discussion revolves around a physics problem involving work done by a spring and kinetic energy (KE). Participants explore the relationships between potential energy, kinetic energy, and the effects of changing displacement in a spring system.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the derivation of velocity from energy equations, questioning the implications of doubling displacement on velocity and height. There are attempts to clarify the relationships between different forms of energy in the system.

Discussion Status

Some participants have provided guidance on organizing the work better and clarifying the relationships between energy forms. Multiple interpretations of the energy conservation equations are being explored, with some participants correcting terminology and concepts.

Contextual Notes

There are discussions about the assumptions made regarding energy conservation and the conditions at maximum height, as well as the correct use of terminology in the context of physics problems.

Lori

Homework Statement



upload_2017-11-8_13-48-5.png

Homework Equations



W= KE
Wspring = .5kx^2

The Attempt at a Solution


since W = .5mv^2 = Wspring = .5x^2
i solve for v and get that v = sqrt(kx^2/m)
if i plug in multiply the x by 2, the 2 squares and i get 4. the square root of 4 is just 2 and it comes out as a constant , and so velocity is 2 times faster

Did i go through the problem correctly?[/B]
 

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Lori said:

Homework Statement



View attachment 214618

Homework Equations



W= KE
Wspring = .5kx^2

The Attempt at a Solution


since W = .5mv^2 = Wspring = .5x^2
i solve for v and get that v = sqrt(kx^2/m)
if i plug in multiply the x by 2, the 2 squares and i get 4. the square root of 4 is just 2 and it comes out as a constant , and so velocity is 2 times faster

Did i go through the problem correctly?[/B]

You got the right answer for the right reasons. You might like to think, however, about how you could organise your working better.
 
Lori said:

Homework Statement



View attachment 214618

Homework Equations



W= KE
Wspring = .5kx^2

The Attempt at a Solution


since W = .5mv^2 = Wspring = .5x^2
i solve for v and get that v = sqrt(kx^2/m)
if i plug in multiply the x by 2, the 2 squares and i get 4. the square root of 4 is just 2 and it comes out as a constant , and so velocity is 2 times faster

Did i go through the problem correctly?[/B]
You are right but if you have to write what is relation between heights
 
Abhishek kumar said:
You are right but if you have to write what is relation between heights
mgh + 1/2mv^2=PE of Spring + mgh
mgh + 1/2mv^2 = .5kx^2 + 0
mgh + .5mv^2 = .5k(2x)^2
mgh + .5mv^2 =4 (.5kx^2)

since m and g are constant in the left side of the equation, the coefficient 4 will affect the height and the speed of the object and the final KE
height will be 4 times as big and the velocity would be twice as fast at final, while the final KE will times 4
 
Lori said:
mgh + 1/2mv^2=PE of Spring + mgh
mgh + 1/2mv^2 = .5kx^2 + 0
mgh + .5mv^2 = .5k(2x)^2
mgh + .5mv^2 =4 (.5kx^2)
height will be 4 times as big and the velocity would be twice as fast at final
When block will reach its maximum height velocity will be zero at that instant simply applying energy conservation at that instant you will get the result
 
Abhishek kumar said:
When block will reach its maximum height velocity will be zero at that instant simply applying energy conservation at that instant you will get the result
How would you write the equation?

How is the one I wrote above incorrect?

In energy conservation E2 = E1

(Final energy) PE2 + KE2 = PE + KE1 (initial energy)
 
Lori said:
How would you write the equation?

How is the one I wrote above incorrect?

In energy conservation E2 = E1

(Final energy) PE2 + KE2 = PE + KE1 (initial energy)
When block reach max height at that instant velocity seized and no kinetic energy
. 5kx^2=mgh
 
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Abhishek kumar said:
seized
Ceased.
 
haruspex said:
Ceased.
Thank you for correcting me
 
  • #10
Abhishek kumar said:
Thank you for correcting me
Oh I see. So in this spring problem. The initial energy comes from PE of spring.

The final energy comes from the gravitational energy since kinetic energy is 0 (because the object stops)
 
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  • #11
Lori said:
Oh I see. So in this spring problem. The initial energy comes from PE of spring.

The final energy comes from the gravitational energy since kinetic energy is 0 (because the object stops)[
Lori said:
Oh I see. So in this spring problem. The initial energy comes from PE of spring.

The final energy comes from the gravitational energy since kinetic energy is 0 (because the object stops)
Yes you got it
 

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