During the construction of a high rise building, 40-kg block is vertically lifted 20 meters from the surface of the earth. To one significant figure, what is the change in the gravitational potential energy of the block?
A)+800 J
B)-800 J
C)+8000 J
D)-8000 J
E)zero joules

Question

Quizplus · Accepted Answer

The change in gravitational potential energy is given by the formula:

ΔU = mgh

where:
ΔU = change in gravitational potential energy
m = mass of the block
g = acceleration due to gravity
h = height change

Substituting the given values:

ΔU = (40 kg)(9.8 m/s²)(20 m) = 7,840 J

Rounding this value to one significant figure, we get:

ΔU ≈ +8000 J

Therefore, the best choice is C, which is +8000 J.

During the Construction of a High Rise Building, 40-Kg Block