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Racheal Haley

on 29 October 2014

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Transcript of WORK and POWER!


What is work?
Work is a force that causes an object to move some distance
in the direction that the force is applied!

However, applying force WITHOUT moving a distance yields NO WORK!

How do I calculate work?
Work = Force x Distance
W=F x d
What if I know the amount of work but need to find the other variables?
Just like our other equations, sometimes you will need to solve for other variables like F or d.
Great! I understand work...but what is POWER?
Power is how quickly work is done!
Let's calculate POWER!
Example: If it takes you 10 s to do 150 J of work on a box to move it up a ramp, what is your power output?
How can you determine if work is being done?
Which of the following are actually considered work? (Hint think about the direction of the force and the direction of the motion!
We know that force is measure in Newtons. We also know that distance is measured in meters. Therefore, when you multiply, you get a unit known as the Newton-meter.
One Nm is equal to one joule. A joule is the unit used to express energy. Because work is a transfer of energy, we use joules to measure it!
Example Problem:
How much work is done when an 8 N force moves a block 7 m?
W= F x d
W= 8 N x 7m = 56 Nm or 56 J
Your Turn! Write each problem on pg 79 and solve it in your science notebook!
1. Evan applies 40 N of force to move her bookcase 3m. How much work did she do?
W = F x d = 40 N x 3 m = 120Nm or 120 J
2. How much work is done by a crane that lowers 1000 N of material a distance of 150 m?
W = F x d = 1000N x 150 m= 150,000 Nm or 150, 000 J
W = F x d or F = W/d or d=W/F
1. How
490 J
of work raise a block weighing
W= F x d --> d= W/F
d= 490J/7N = 490
= 70 m
2. Emma does 110 J of work to move a chair 2 m to the right. How much force was required to do this?
W = F x d --> F = W/d
F = 110 J/2m = 110 Nm/2 m = 55 N
When you calculate power, you divide the amount of work done by the time it takes to do that work.
P = W/t
We know that work is calculated in Joules. And we know that time is measured in seconds. When you calculate power, you get J/s which is the same thing as a watt.
A watt (W) is equal to 1 J/s
P = W/t = 150J/10s = 15 J/s or 15 W
Full transcript