Question

A backpack has a mass of 8 kg. It is lifted and given 54.9 J of gravitational potential energy. How high is it lifted? Acceleration due to gravity is g = 9.8 m/s2.

Answer 1

Potencial Energy=hma
Where
Potencial Energy =E= 54.9J
h=?
m=8kg
a=9.8m/s^2
You need to know that 1 J=1(kgm^2)/s^2

Isolate h=E/(ma)
h=(54.9)/(8*9.8)

Answer 2

Answer: The potential energy for a lifted object is U = m*a*h

where m is the mass, h is the height and a is the acceleration.

in our problem the mass is m = 8kg, the height is the thing we want to find, a is the gravitational acceleration, 9.8 m/s^2 and U = 54.9j

then our problem is:

54.9j = h*9.8*8 kg*m/s^2

then h = 54.9/(9.8*8) = 0.7m

Then the backpack is lifted 0.7 meters.