formula problem, please help!

[Janarleen3831]

Hi,
I have been doing kaplan and AAMC tests so far. However, while reviewing my kaplan tests, I have found two formulas that are different from the ones that Dr.Ferdinand posted in the formula sheet and I am just confused about that. THe first one I got from the physics dvd which was for simple harmonic motion. I copied down from the video that T=2 pi (square root of l/g). In the kaplan tests, the formula they used for simple harmonic motion was T= 2 pi (square root of m/k). The other forumla came from the formula sheet here that talked about linear expansion. Here its L=Lo (1+alpha(change in temp). In kaplan, they use the formula change in L=alpha(Lo)(change in temp). The formulas look similar so Im not sure if they are just derivations of the same formula. If you could please explain this discrepancy to me that would be really helpful. Thanks so much!

[ayushman80]

T=2 pi (square root of l/g) is the equation for the period of a PENDULUM. "l" is the length of the pendulum and "g" is the acceleration of gravity.

T= 2 pi (square root of m/k)is the equation for the period of an object undergiong SHM on a spring. "m" is the mass of the object on the spring and "k" is the spring constant.

The important thing to get out of these equations is that the restoring force term goes on the bottom (i.e. if gravity or k are increased then period is shortened). Also that the thing that will cause an increase in inertia goes on the top (i.e. a larger m and l would be more difficult to move for a given force and therefore increase the period of motion).

D don't believe that you have to memorize the thermal expansion equations. But understand that if you heat something it will get bigger and shrink if it gets colder. Its more likely that you will be given those equations.

[ayushman80]

T=2 pi (square root of l/g) is the equation for the period of a PENDULUM. "l" is the length of the pendulum and "g" is the acceleration of gravity.

T= 2 pi (square root of m/k)is the equation for the period of an object undergiong SHM on a spring. "m" is the mass of the object on the spring and "k" is the spring constant.

The important thing to get out of these equations is that the restoring force term goes on the bottom (i.e. if gravity or k are increased then period is shortened). Also that the thing that will cause an increase in inertia goes on the top (i.e. a larger m and l would be more difficult to move for a given force and therefore increase the period of motion).

D don't believe that you have to memorize the thermal expansion equations. But understand that if you heat something it will get bigger and shrink if it gets colder. Its more likely that you will be given those equations.

[Janarleen3831]

Thanks so much. That really helped me alot! Best of luck on your upcoming mcat!

[admin]

I agree with the above; including the fact that it is very unlikely that you would be expected to memorize the thermal expansion equations. This is why in our equation list, we have put those equations under the title Don't Memorize, Know How to Use:

www.goldstandard-mcat.com/physics-equation-lists/