Honors Assignment

For section 2 do the energy assignments that section3 did the other day see earlier posts.

For everyone:

1) Read these notes, they will help you a great deal. Do not worry about losses for now or about forces not in same direction as distance traveled.

http://h1.ripway.com/DrCherdack/Notes%20%20Work%20and%20Energy%20R5.doc

2) Do the following problems [You can use the following equation

change in position = (vfinal squared - v initial squared)/(2 x acceleration)

to find the final velocity if you rewrite it for vfinal =.....(you figure it out)....


for falling objects and any other time you do not know vfinal]
(use g =10 for the acceleration of an object in free fall on earth )

1) A 4 kg flower pot falls off a shelf 3 m above the ground. How fast is it going just before it hits the ground? What is its KE. Compare it with Mass x g x change in height. Is this the work done by gravity on the pot? Is it equal to the loss in PE?

2) A 1500 kg car accelerates from zero to 20 m/s in 4 seconds. About how far did it travel ?( Figure out v average from vinitial and v final and use it to find how far the car went in 4 seconds.) What was the net force on it to cause this acceleration. Given Fnet and distance, how much work was done? What was the final KE? Are the work done and KE equal.

3) If you lift a 20 kg crate 12 m how much work did you do? How much PE did the crate gain? How fast will it be going if it falls back the 12 m? How much KE will it have gained falling the 12 m? Does this match the PE lost?