Work!!

Take 5….

• With your partner, write a definition for work.

• Examples:1)

2)

• Be prepared to share…

Who’s doing more work?

Worksheet time!

• Complete the first half of the worksheet….

• You have approximately 10 mins…

Who’s doing more work?

Defining Work

• Okay….so what is work?– Product of force AND displacement– Conditions for work:

• A force must be applied.• The force has to make the object move in the direction

of the applied force

• Examples:1)2)

Formula Time!!

• Work = Force x Distance– (J=F*d)

• Force = work / distance– (F = w/d)

• Distance = work / Force– (d = w/F)

UNITS

• Force : Newton (N)– A newton is the force required to accelerate a 1

kilogram mass at 1 meter/second2. • Displacement: Meters (m)• Work: Joule (J)

– A Joule is a force of 1 Newton exerted through a distance of 1 meter does one joule of work, or in other words, J = N x m.

• What is the direction of force?• What is the direction of the motion?• Any force that does not act in the direction of

motion does no work on an object… 70 N 40 N

30 N

Direction of motion

A boy is pushing a rock with a force of 45 Newtons. The rock doesn’t move. How much work has the boy in the figure done?

Work = F x d 45 N x 0 m = 0 J

A boy pushed a shopping cart a distance of 3 meters doing 15 J of work.

How much force has the boy applied?

F=w/d 15J/3m= 5N

Objective

1. Compare the direction of the object’s motion to the direction of the applied force

2. Describe the distance when no work is done

3. Calculate work, force and distance given two of the three

Did we meet the objectives?

1.If you exert a force of 10.0 N to lift a box a distance of 0.9 m, how much work do you do?

a. 0.1 Jb. 9.0 Jc. 10.9 Jd. 90.0 J

Did we meet the objectives?

• 2. In the movie Independence Day, Will Smith drags an alien across the dessert. True or False all of the force (in this case the force is diagonal) Will is applying to drag the alien does work.

Did we meet the objectives?

3) Which of the following is true?a) only the x axis component (part) of a force does workb) motion is in the direction of applied forcec) both a & bd) none of the above

Did we meet the objectives?

4) Which of the following statements are truea) A weight lifter does a lot of work because the

barbell is heavy!b) The weight lifter does a lot of work because I

said soc) The weight lifter does no work because there is

no distance d) Idk