1015

• Run Multiple Choice Generator at h:\shares\physics
• Run Core Problems by giving the program qzz as your 'course'--enter this when asked for your 3-digit course number.   Do the Physics Quiz 1013.
• If you miss a problem be sure to click on Comment and explain what you do and do not understand about the question and the given solution.

Homework:  Chapter 6 as assigned on Assts page or as specified below. 

Problems for 6th Edition of Giancoli:  15, 19, 27, 31, 36, 37, 38, 41, 42,  47, 48, 53, 62, 66

From last week's experiment:

From the projectile behavior of the stick figure out how much KE the stick attained as a result of the action of the rubber band.

The projectile behavior is analyzed by figuring out how long it takes to fall the vertical distance and dividing this into the horizontal displacement.

Assuming that the stick attained the same KE for each pullback on the tabletop figure out the average force exerted by friction, and express the average force as a percent of the weight of the stick.

After release the KE is whatever we got from the preceding result. 

The net force acting on the system is the frictional force.  We know the displacement and we know the change in KE, and we have the work-energy theorem.  Put these together to find the force exerted by friction.

Then find the percent as requested.

From the 10/06 Experiment:

We were to find:

• the work required against gravity to raise the ball from the bottom of the ramp to the top of the ramp
• the KE of the ball at the end of the ramp
• the percent of the work required to raise the ball represented by the ball's KE at the end of the ramp

From your results and the length of the ramp determine the average net force on the marble on each ramp.

Graph average net force vs. ramp slope.

`dWnetBy + `dKE = 0

Since the net force can have conservative and nonconservative parts (conservative forces store the energy, like a stretched rubber band or an object held above the floor in a gravitational field), we split `dWnetBy into `dWnetByConservative and `dWnetByNonconservative and get

`dWnetByConservative + `dWnetByNonConservative + `dKE = 0

or

`dPE + `dWnetByNonconservative + `dKE = 0, often expressed as

`dPE + W + `dKE = 0,

where in a sparkling example of clarity it's left for you to remember that W is the work done by the system against conservative forces.