9. Suppose you want to calculate how much work it takes to lift a 160 N barbell. Besides
the mass of the barbell, what other
information do you need to know?
a. the shape of the weights
b. how high the barbell is being lifted
c. the strength of the person doing the lifting
d. the volume of the barbell

The correct option is;

b. How high the barbell is being lifted

Explanation:

The work done in lifting the 160 N barbell is equal to the potential energy gained by the barbell in the final elevated position of the barbell

Therefore, in order to find the work done to lift the barbell, we can calculate the potential energy gained by the barbell when it is placed at height

The work done to lift the barbell = The potential energy, P.E., gained by the barbell

The potential energy of an object, P. E. = The mass of the object, m × The acceleration due to gravity, g × The height to which the barbell is lifted, h

∴ Mathematically, P.E. = m × g × h

Weight, W = Mass, m × The acceleration due to gravity, g

The weight, W of the barbell is given as W = 160 N

∴ W = m × g = 60 N

From which we have;

P.E. = m × g × h = W × h

∴ The work done to lift the barbell = P.E. = 60 N × h = 60 N × The height to which the barbell is lifted.

Therefore the information which need be known is the height to which the barbell.

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