Physics 11 Force and potential energy

[Iceclover]

Homework Statement

A constant net force of 410N up is applied to a stone that weighs 32N. The upward force is applied through a distance of 2.0m andthe stone is then released. TO what height from the point of release will the stone rise?

Homework Equations

Ep=mgh

The Attempt at a Solution

Ep=mgh
410=32(h)
h=13m

 

[mbrmbrg]

I'm not sure where you're going with your solution.
Personally, I'd apply impulse again to get the stone's final velocity at the time of release, and then treat it as one-dimensional motion with constant acceleration.

 

[Iceclover]

i can't use impulse can I? i don't have a time?

 

[mbrmbrg]

Picky, picky...

OK, how about the Work-Energy theorem to find the velocity at release?

 

[Iceclover]

Ek=1/2mv^2? and which force do i use

 

[mbrmbrg]

Ek=1/2mv^2?

Ah, no. Can you state the Work-Energy Theorem? (If not, can you look it up in your textbook or notes?)

 

[cristo]

An easier way is to use the Work-Energy Theorem, as stated above. Calculate the work done by the force on the stone for the 2m that it is applied (recall, work done = force * distance). When the stone reaches its maximum height, all the energy is the potential energy, so you can equate the potential energy to the work done, and solve for h.

 

[Iceclover]

Work done on object is equal to the change in its kinetic energy

 

[mbrmbrg]

OK, so can you apply it? (I know I can...)

 

[Iceclover]

what do i do once I've found velocity

 

[mbrmbrg]

Use a basic kinematics equation for motion with constant acceleration.

 

[Iceclover]

the answer i got was 26m

 

[mbrmbrg]

Oddly enough, so do I.

 

[Iceclover]

ok good, thank you very much

 

[Iceclover]

do you have time for another question?

 

[mbrmbrg]

Not really... but I'm in the middle of studying for my physics final, so this helps me, too. Look, If I don't answer, someone else will. (That's why this forum rocks!)

 

[Iceclover]

ok sounds good, i think I am going to make a new topic though