1. The Work Energy Theorem
Textbook:
Homework: pg. 183 # 2, 5, 6, 7 pg. 188 # 2, 5, 6, 7, 8
pg. 194 # 1 – 7

3. Work
Work is the energy transferred to an object by a force F, through a displacement d
W=Fdcos
W = [J], F = [N], d = [m]
James Prescott Joule (1818 – 1889):
English physicist
Discovered relationship btw. heat & mechanical work (energy)
Conservation of Energy Theorem

5. Mechanical Energy is a combination of two fundamental types of energy:
Kinetic energy (the energy of motion)
Potential energy (energy that is stored) - Gravitational Potential Energy
- Elastic Potential Energy

6. Kinetic Energy Work done by the net force causes a change in speed
The kinetic energy of an object of mass m, in kg, and speed v, in m/s:
Pg. 226 #3
Pg. 242 #

7. Gravitational Potential Energy
“stored energy” in an object at a particular height w.r.t. a reference point.
Ex. Pg. 191 #1, 2, 3
Ex. Pg. 194 #7

8. W.E.T. (Work-Energy Theorem)
The total work done on an object equals the change in the object’s kinetic energy and/or gravitational potential energy.
Ek = -Eg

9. Ex 1: By what factor does a cyclist’s kinetic
Ex 1: By what factor does a cyclist’s kinetic energy increase if the cyclist’s speed:
(a) doubles
(b) triples
(c) increases by 37%

10. Ex 2. A 45-g golf ball leaves the tee with a speed of 43 m/s after a golf club strikes it.
(a) Determine the work done by the club on the ball.
(b) Determine the magnitude of the average force applied by the club to the ball, assuming that the force is parallel to the motion of the ball and acts over a distance of 2.0 cm.

11. A 27­g arrow is shot horizontally
 A 27­g arrow is shot horizontally. The bowstring exerts an average force of 75 N on the arrow over a distance of 78 cm. Determine, using the work­energy theorem, the maximum speed reached by the arrow as it leaves the bow

12. Elastic Potential Energy & Conservation of Energy
Pg. 211 #8
Textbook: 4.5
Homework: WS – Spring problems

13. What is Hooke’s LAW
A Hookean System (i.e. spring, wire, rod etc) is one that returns to its original configuration after being distorted and then released.

14. Hooke’s Law …cont Fapplied on spring Slope = k = spring constant
x, (i.e distance from equilibrium)

15. Potential Elastic Energy
Fapplied on spring
Work
done
x, (i.e distance from equilibrium)

16. Elastic Potential Energy
The energy stored in a spring of spring constant k [N/m] compressed or extended from equilibrium a distance x [m] is:
Pg #
Derive formula for Pendulum (Restoring Force)
Relate to period of a spring and mass system
Pg #16, 18

17. The Law of Conservation of Energy
Energy cannot be created or destroyed, but only transferred from one form to another without any loss.
The total energy of a closed system is constant.

18. Elastic Potential Energy & Simple Harmonic Motion (SHM)
Pg. 211 #8
Textbook: 4.5
Homework: pg # 16 – 21
pg # 23 – 28

19. Simple Harmonics Motion (SHM)
Motion that obeys Hooke’s law
Periodic and follows sinusoidal function

20. Period of SHM

21. SHM & Damping: The effect of friction on SHM is called damping.
Three Types of Damping: 1) Overdamping: Oscillation ceases and the mass slowly returns to equilibrium position 2) Critical damping: Oscillation ceases and the mass moves back to equilibrium position as fast as theoretically possible without incurring further oscillations. This special point is never perfectly reached in nature 3) Underdamping: Oscillation is continually reduced in amplitude
Decreasing amplitude
“Envelope” of the damping motion

22. Pg 214 # 18.