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Gravity and Spring + KE problem

Thread starter Lori
Start date Nov 8, 2017
Tags

Gravity Spring

3 replies · 1K views · last reply Nov 8, 2017

Lori

Thread starter
Nov 8, 2017

#1

Homework Statement

Handwritten energy derivation annotating a spring-and-pulley diagram: W_S = -1/2 k x^2 = -1/2(380)(0.4)^2 = -30.4, W_b = 20(9.8)(0.4) = 78.4, E_T = W_S + W_b = 78.4 - 30.4 = 1/2 m v^2, v = 2.2.

Homework Equations

shown above

KE = .5mv^2
KE = Total Work
Total work = Work by block - work by spring

The Attempt at a Solution

Shown above.

Did i do the problem correctly? I'm always unsure if I am doing the problem right

Discussion

haruspex

Science Advisor

Homework Helper

Insights Author

Gold Member

Nov 8, 2017

#2

Looks right.

Abhishek kumar

Nov 8, 2017

#3

Lori said:

Homework Statement

View attachment 214620

Homework Equations

shown above

KE = .5mv^2
KE = Total Work
Total work = Work by block - work by spring

The Attempt at a Solution

Shown above.

Did i do the problem correctly? I'm always unsure if I am doing the problem right

Yes this is right but you made this free body diagram comparing force with work done

haruspex

Science Advisor

Homework Helper

Insights Author

Gold Member

Nov 8, 2017

#4

Abhishek kumar said:

Yes this is right but you made this free body diagram comparing force with work done

Good point.

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