THIS PAGE WILL BE GONE IN 5 mins BE SURE TO HAVE YOUR ID VISIBLE AROUND YOUR NECK, NO NON- POLY ATTIRE! DRILL: WORKDate: Jan 23, 2012 Define work in your own terms. OBJECTIVE Define work in physics and calculate work done in a system. HOMEWORK Copy and answer no. 15 & 20 of page 265

THINK ABOUT! Which is work, reading and studying or playing football?

Tops the Sem Exam 1 st MARTIN – 81% 2 ND NICHOLSON – 76% 3 RD DICKERSON – 68%

Tops the Sem Exam 1 st QUACH – 94% 2 ND SCRIBNER – 89% 3 RD CRAFTON – 85%

Tops the Sem Exam 1 st AYBAR – 100% 2 ND HUGHES – 93% 3 RD SRAHA – 80%

Tops the Sem Exam 1 st OGUNFIDITIMI – 86% 2 ND DIALLO – 82% 3 RD ODOMS – 78%

Tops the Sem Exam 1 st GODFREY – 85% 2 ND SOKO – 78% 3 RD HOGAN – 69%

8 What is work? The scientific definition of work is: using a force to move an object a distance !!! both the force and the motion of the object are in the same direction

Work or Not? According to the scientific definition, what is work and what is not? –a teacher standing on the same spot as she is lecturing to her class –a mouse pushing a piece of cheese with its nose across the floor Not work work

10

11 What’s work? A scientist delivers a speech to an audience of his peers. A body builder lifts 350 pounds above his head. A mother carries her baby from room to room. A father pushes a baby in a carriage. A woman carries a 20 kg grocery bag to her car? Not work work work

12 Formula for work Work = Force x Distance The unit of force is newtons The unit of distance is meters The unit of work is newton-meters 1 Nm = 1 Joule So, the unit of work is a joule

13 W=Fd If a man pushes a concrete block 10 meters with a force of 20 N, how much work has he done? (W = 20N x 10m) W = 200 joules W = 200 joules

PRACTICE PROBLEM Which requires more work, carrying a 420-N knapsack up a 200-m hill or carrying a 210-N knapsack up a 400-m hill? W1 = F1 d1 = 420 N x 200 m = J or 84 Kj W2 = F2 d2 = 210 N x 400 m = J or 84 kJ

CLASSWORK PART 1: In YOUR NOTEBOOK, ANSWER ONLY…. SHOW WORK ON PROBLEMS: --- Label no. properly---- NOs. 1, OF PAGE 241 Nos OF PAGE 242 PART 2: Answer the worksheet provided [will be collected]

WRAP-UP Copy and answer OR answer in a complete sentence How is the definition of work in physics and in ordinary terms different? REMINDERS! Only absences/ missed work with pink slips can be made up MISSING A DETENTION = 0 IN ALL OUTPUTS FOR THAT DAY [includes notebook] COACH CLASS Tues & Thurs AFTER SCHOOL IN RM 127 NO COACH CLASS TODAY

Main Menu WHY??? Work is done on the books when they are being lifted, but no work is done on them when they are being held or carried horizontally. WHY???