WORK AND POWER

WHAT IS WORK?

When you do real work, you get tired. If you are smart, however, just exerting forces, shouldn’t get you tired.

Does holding a rubber band stretched get you tired?

What if you used a stick or a pencil to hold the rubber band stretched?

Do you think you are doing work when you hold a rubber band in a stretched position?

REMEMBER! You are just HOLDING it and you are

NOT MOVING either hand.

WORK! WORK! WORK!

Formula:

WORK = Force x Displacemente.g.

5 m

W = F x d = (10 N)(5 m) = 50 N.m or 50 J

10 N

Is he doing work?

Work? Or NOT Work?

Example problem:

Renatta Gass is out with her friends. Misfortune occurs and Renatta and her friends find themselves getting a workout. They apply a cumulative force of 1080 N to push the car 218 m to the nearest fuel station. Determine the work done on the car.

POWER

Power is the rate of doing work.

Power is work per time.

Formula:

Unit of Power

Power

The metric unit of power is the Watt

Example:

Ana weighs 50N and Lara weighs 35N. Mark carries each of them at 30 seconds and 20 seconds respectively. How much power does Mark apply to both of them if he carries each of them from a distance of 12 m?

Given: Ana’s weight: 50N Lara’s weight: 35N D: 12m

Solution:

Power = W/t Power = (F.d)/t Ana:

P = (50N x 12m)/30 s

= 600Nm/30s

= 20 Nm/s or 20 J/s

= 20 Watts

Other examples…

Interactive solving