posted by Anna .
A 4.3 "kilo" bag of sugar is on a counter. How much work is required to put the bag on a shelf a distance of 0.43 m above the counter?
There are only two pieces of information given here: mass and distance. So, look in your text for problems involving work, mass, and distance.
Hooray! We find that work is the same as the change in energy. Hmmm. Now what. Potential energy is just force times distance.
So, we have mass and distance. We want force and distance. So, what are we doing? Moving mass upwards against gravity. Aha! In such an instance, F = ma = 9.8*m
Good old formula: W = mgh
Now we have the work is just the potential energy gained moving a 4.3kg mass for 0.43 in a gravity field.
W = mgh = 9.8 * m * 0.43 = 4.2 Nm = 4.2J