Mechanics clarification needed (EPE)
Maths and statistics discussion, revision, exam and homework help.
-
- Reputation:
- Thread Starter
- Benevolent Member
- Posts: 858
Mechanics clarification needed (EPE)Hi,
During A Levels in M3 were taught that the change in EPE was equal to final E.P.E. - initial E.P.E, which is equal to λy²/2L - λx²/2L as mentioned on chapter 2 of this page:
http://www.thestudentroom.co.uk/showthread.php?t=771543
However, at uni we are now taught that in stretching a spring or string, the tensile force is equal to kx (which we were told at A Level physics) and the work done in stretching an elastic spring is kx²/2 (integral of force is work done) which translates to λx²/2 if k and λ are the same thing (both modulus of elasticity). Now, λx²/2L and λx²/2 are not the same thing so was wondering if i'm missing something obvious here...Therefore the work done in stretching an elastic spring with modulus λ from its natural length L to a length (L+x) is λx²/2L
Can anyone help me understand? -
- Reputation:
- TSR Demigod
- Posts: 5,512
Re: Mechanics clarification needed (EPE)In physics we study,(Original post by Like_A_G6)
Hi,
During A Levels in M3 were taught that the change in EPE was equal to final E.P.E. - initial E.P.E, which is equal to λy²/2L - λx²/2L as mentioned on chapter 2 of this page:
http://www.thestudentroom.co.uk/showthread.php?t=771543
However, at uni we are now taught that in stretching a spring or string, the tensile force is equal to kx (which we were told at A Level physics) and the work done in stretching an elastic spring is kx²/2 (integral of force is work done) which translates to λx²/2 ifk and λ are the same thing(both modulus of elasticity). Now, λx²/2L and λx²/2 are not the same thing so was wondering if i'm missing something obvious here...
Can anyone help me understand?
In M3 we study,
So
-
- Reputation:
- TSR Demigod
- Posts: 5,512
Re: Mechanics clarification needed (EPE)(Original post by Like_A_G6)
However, at uni we are now taught that in stretching a spring or string, the tensile force is equal to kx (which we were told at A Level physics) and the work done in stretching an elastic spring is kx²/2 (integral of force is work done) which translates to λx²/2 if k and λ are the same thing (both modulus of elasticity). Now, λx²/2L and λx²/2 are not the same thing so was wondering if i'm missing something obvious here...
Much appreciated 
