Docstoc

ENERGY_1_

Document Sample
ENERGY_1_ Powered By Docstoc
					                ENERGY
                    -WORK
              -TRANSFORMATIONS



HTTP://TEACHERTUBE.COM/VIEWVIDEO.PHP?VIDEO_ID
                    =127812
                  Kinetic Energy

 In motion (has velocity)
 ½ mv2
UNIT: Joules

Velocity more than mass
               Potential Energy

 Not moving: contain energy
 In Joules
 Gravitational Potential Energy: mgh
 Elastic Potential Energy:
            Mechanical Energy

 PE + KE
 Work
 Forces change based on Transformation of energy
 Only the force parallel to displacement is doing
  work (NET W=NET F x d x cos angle)
 W=Fd (mass and acceleration of an object in a
  direction times the distance the force is being
  applied)-UNIT: JOULE (Nm)

 DERIVE:        2ad=vf 2-vi2   (Big Blue on the board)
                   Practice Problems

1.   A shopper in a supermarket pushes a cart with a
     force of 35 N directed at an angle 25 degrees
     downward from the horizontal. Find the work
     done by the shopper on the cart as the shopper
     moves along a 50.0 m length of side?

                                     1600 J
1. If 2.0 J of work is done in raising a 180 g apple,
   how far is it lifted?

              1.                 1.1M
                    Work cont….

 Scalar
 Positive-same direction as displacment
 Negative-direction opposite (friction)
                Kinetic Energy!

 Has mass and is moving
 Scalar
 Joule




WORK-KINETIC ENERGY THEOREM:
Wnet=Change in KE            (1/2)
              KE Practice Problems
1. A 7 kg bowling ball moves at 3 m/s. How much KE
   does the bowling ball have? How fast must a 2.45 g
   ping pong ball move in order to the same KE as the
   bowling ball? Is that realistic?
                          KE=31.5 J
                       V = 160 m/s
                             NO
A person kicks a 10 kg sled, with an Vi =2.2m/s. How far
   does the sled move, if the coefficient of Fk b/t the sled
   and ice is 0.1?

                                      2.4 m
                    Potential Energy

 Based on the position relative to another location
 GPE=mgh (only in free fall near Earth)
 EPE=1/2kx2 (relaxed length 
 compressed/stretched length)
    k=spring constant (N/m)
              PE Practice Problems:

1.   A 70 kg bungee jumper has a cord 15 m long. He
     jumps off a bridge from a height of 50 m. When he
     finally stops the cord has stretched to 44 m.
     Bungee cord has a k of 71.8 N/m, what is the total
     PE relative to the water when the man stops
     falling?




2.                                3430 J
 http://videos.howstuffworks.com/

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:3
posted:12/7/2012
language:Japanese
pages:13