1. Friday(11/06): The Concepts of Work, Power, and Energy in Physics.

HW: Read pages 257-265, and Solve prob. 52, 53, 59, 62, and 66 on

pages 278-279.

2. Monday(11/09): Simple machines, Work Input, Work Output, and

Efficiency. HW: Read pages 266-277, and Solve prob. 77, 79, 83, and 84

on pages 280-281.

3. Tuesday(11/10): The Many Forms of Energy. HW: Read pages 285-292,

and Solve prob. 54, 55, 60, and 62 on page 307.

4. Wednesday(11/11): No School due to Veteran's Day. HW: Continue

with assigned work.

5. Thursday(11/12): The Law of Conservation of Energy. HW: Read

pages 293-305, and Solve prob. 64, 66, 67, 77, and 79 on page 307.

6. Friday(11/13): Lab experiment on Pulley Systems. 

HW:  Process lab data. Abstract due Tuesday.

7. Monday(11/16): FCAT Science Diagnostic/Standardized Test Practice.

HW: Complete all Review Handouts.

8. Tuesday(11/17): FCAT Science Diagnostic/Standardized Test Practice.

HW: Complete all Review Handouts.

9. Wednesay(11/18): Post-Lab Discussion and Test Review.

HW:  Complete lab report and write Abstract (Due Thursday).

10. Thursday(11/19): TEST on Chaps.10&11 - Work and Energy.

HW: Go to web-site for notes on Ch.12 - Thermal Energy.

1. Work is done in physics when a force is applied to an object and it

undergoes a displacement in the direction of the force.

2. This definition allows us to calculate Work = Force x Displacement or

W = F·d ,and then it is measured in Newton meters, Nm, or Joules.

3. Work is a scalar quantity, even though Force and Displacement are

vectors, but the Force or at least one of its components must be in the

direction as the displacement.

4. The unit of work, the Joule, was named after the Scottish physicist

James Prescott Joule (1818-1889), who determined the connection

between mechanical work and heat. Recall that 4.19 J = 1 cal.

5. We usually do work against friction when sliding an object, and against

gravity when lifting, W = mgh.

6. When applying a force at an angle, we use the cosine of the angle

to compute the amount of work done, W =(Fcosθ)·d.

7. Energy is the ability to do work, and there are two kinds of energy,

kinetic and potential.

8. Kinetic energy is due to mass and velocity, KE = ½mv² .

9. Potential energy is due to an objects position, PE = mgΔy ,

gravitational.

10. Potential energy can also be elastic, PE = ½kx² , with k being the

spring constant, k = F/m.

11. Work can also be computed by finding the area under a Force vs

Displacement curve.

12. Work can also be explained as the transfer of energy by mechanical

means. Mechanical energy is the total kinetic and potential energy

present in a given situation.

13. There is a conservation law for energy which states that "energy can

change in form but can never be created or destroyed, only changed in

form", or KE_i + PE_i = KE_f + PE_f.

14. Neglecting friction, mechanical energy is conserved, so that the total

amount remains constant.

15. The net work done on or by an object is equal to the change in the

kinetic energy of that object. This means that W = ΔKE = KE_f - KE_i .

16. Power is the rate of doing work, P = W/t , or P = F·d/t , or even

P = F·v_avg and is measured in Watts.

17. The Watt was named after James Watt (1736-1819) from Scotland,

who perfected the steam engine and made it practical to use.

18. Power is also the rate at which energy is transferred, with 1000 watts

being, of course, a kilowatt, kw.

19. Machines with the same power ratings in watts do the same amount of

work in different time intervals.

20. There are six simple machines: pulley, inclined plane, wheel and axle,

jackscrew, lever, and wedge. For each we can compute the Mechanical

Advantage, Ideal Mechanical Advantage, Work Output, Work Input, and

an Efficiency. We will derive the equations for these.

21. And still, we need these steps to solve any problem in Physics:

(i) read the problem and identify the given variables

(ii) determine what you are asked to solve for

(iii) find the correct motion formula to use

(iv) use algebra to isolate the unknown

(v) substitute-in the given information and simplify.

Here are the answers to the homework problems:

Page 278-9:

#52. 1x10⁴ J  #53. 59.9 kg

#59. 9.00 kJ, 3.00 kW       #62. 36.2^o 

#66. 1.20x10⁴ J

Page 280-81:

#77. 2300 N   #79. 300 n, 40 N, 6000 J, 6800 J, 3.5  

#83. .24 m    #84. 1.64x10⁴ J  

Page 307:

#54. 1.3x10⁵ J  #55. (a) 6.86x10⁵ J

#60. 66 m       #62. 2.1x10³ J 

Page 308-9:

#64. -2.78x10³ J  10 m/s  #66. 20.0 m 

#67. 17 J       #77. 9.39 m/s    #79. 39.4 m

THE HONORS PHYSICS ARCHIVES Ch.1: Physics Intro. Ch.2&3: Linear Motion. Ch.4&5: Forces. Ch.6: 2-Dim Motion. Ch.7: Gravitation. Ch.8: Rotary Motion. Ch.9: Momentum. Ch.10&11: Work&Energy. Ch.12: Thermal Energy. Ch.13: States of Matter. Semester Review.