inn what situations can we not apply hookes law?? like i got a question wrong bc i used hookes law instead of es=1/2kx^2 to find k. some thing to do with energy? it was about a trampoline and calculating k of trampoline. does this mean that w=fd would not apply either? why??

Hi Mego,

If you can you tell me which question it was or provide the wording of the question I will give you a more specific response.

In general, the information you are given in the question should determine which equation would apply. In some situations the force stretching or compressing the object may not be vertical, so an incorrect assumption about weight providing your Force value may lead to an incorrect answer for k, however, this seems unlikely for a question about a trampoline. If the object on the trampoline was stationary, then we would expect weight force to equal the restoring force of the trampoline, and F=-kx using a value equaly to weight force should apply. For NCEA Level 2, I’m really struggling to think of a trampoline question in which you couldn’t use either equation.

No brain too small has a great collection of exam questions and answers that might help build your confidence.