SOLUTION: The work W required to lift an object varies jointly with the object's mass M and the height H that the object is lifted. The work required to lift a 120-kilogram object 1.8 meters

Question 1190542: The work W required to lift an object varies jointly with the object's mass M and the height H that the object is lifted. The work required to lift a 120-kilogram object 1.8 meters is 2,116.8 joules. Find the amount of work required to lift a 100-kilogram object 1.2 meters.

Found 2 solutions by math_tutor2020, greenestamps:
Answer by math_tutor2020(3817) (Show Source): You can put this solution on YOUR website!

k = some constant
W = work required to lift the object
M = mass
H = height of the object

The second sentence gives this info:
W = 2116.8 joules
M = 120 kg
H = 1.8 m

Use that info to determine k
W = k*M*H
2116.8 = k*120*1.8
2116.8 = k*216
216k = 2116.8
k = (2116.8)/(216)
k = 9.8

Then we can determine W if M = 100 kg and H = 1.2 m

W = k*M*H
W = 9.8*M*H
W = 9.8*100*1.2
W = 1176

Answer: 1176 joules

Answer by greenestamps(13203) (Show Source): You can put this solution on YOUR website!

The other tutor uses the equation of variation and the given data to find the constant of variation k, then uses that constant with the new data to find the new amount of work.

That is of course a sound way to solve the problem; and you would want to work it that way if you were going to find the amount of work for several other sets of data.

But you don't need to go to all that work if all you need to do is find the answer to this one question.

Work for the given data: 2116.8 joules
ratio of new weight to old weight: 5/6
ratio of new distance to old distance: 2/3

ANSWER:

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