Lesson 7
Energy and Simple Harmonic Motion

 Name:ETP Section:M2 Start Time:8:49:37 Instructor:pate Course:355

1) In general, how would you determine whether or not an object is in equilibrium? Also, if it is in equilibrium, how would you determine if it is in stable or unstable equilibrium?

Now consider the case shown in the figure. A cube of uniform density and side length b is on an incline of angle q. At this instant, the side closest to the ramp makes an angle a with respect to the ramp. Don't do the calculation, but describe how you would determine the condition under which the block would be in equilibrium, and whether or not that equilibrium would be stable. (Try to be specific in your description. Exactly what would you do and/or consider?)

2) Your neighbor back at home wants to build a "bouncey seat" for a one year old toddler. The idea is that, once in the seat, the child should be able to extend her legs downward (through holes in the seat) to just reach the floor. If she then pushes her feet firmly against the floor, she should cause herself to bounce up and down (much to her delight!).

The seat is going to be held to the frame with two springy cords. Your neighbor has asked for advice about the cords. What would be a reasonable value of "k" to choose for the cords?

3) Your instructor has been at it again. A Physlet page demonstrating the motion of a mass on the end of a spring has been put together just for you!

Which quantity is being graphed as a function of time?

Note: To obtain your answer, you'll need to look at the Physlet page. Important: This page will open in a NEW window, so you'll need to come back to THIS window (using the taskbar) to submit your preflight. Once again, if the physlet page does NOT load properly, please tell me what happens, including any error messages it displays, in the comments box below. Thanks. Click this link to get to the Physlet page.

1. position
2. velocity
3. potential energy
4. kinetic energy

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