What is the potential energy of a board placed on the edge of a roof?

AI Thread Summary
The potential energy (PE) of a board weighing 22 lb placed on the edge of a roof 28 ft high is calculated using the formula PE = mgh. The correct value for gravitational acceleration in feet is 32.2 ft/sec², not 9.8 m/sec². Using the correct value, the potential energy is calculated as 22 lb * 32.2 ft/sec² * 28 ft, resulting in a potential energy of 12,179.2 ft·lb. This highlights the importance of using consistent units in calculations. The discussion emphasizes the need for accuracy in applying physics formulas.
lilaznjewel
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Homework Statement


A carpenter places a board weighing 22 lb on
the edge of the roof 28 ft above the ground.
How much potential energy does the board
have in relation to the ground?
Answer in units of ft · lb.


Homework Equations


PE=mgh


The Attempt at a Solution


I followed the formula 22*9.8*28 and i got 6036.8
 
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lilaznjewel said:

The Attempt at a Solution


I followed the formula 22*9.8*28 and i got 6036.8
You are using 9.8 m/sec^2 for g. You have use 32.2 ft/sec^2 when you use units of feet and lbs.

AM
 

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