Homework Sourseif the PE of a box on a shelf at h20m above the floor is 200
if the PE of a box on a shelf at h=20-m above the floor is 200J, and the box is pushed off the shelf, what are the KE and PE of the box when it reaches h= 10-m ?
if the PE of a box on a shelf at h=20-m above the floor is 200J, and the box is pushed off the shelf, what are the KE and PE of the box when it reaches h= 10-m ?
if the PE of a box on a shelf at h=20-m above the floor is 200J, and the box is pushed off the shelf, what are the KE and PE of the box when it reaches h= 10-m ?
Solution
We will assume the height h = 0 m as the reference while solving the given problem. It needs to be understood that in absence of any external source of energy, the total energy of the box will remain constant.
We will equate the total energies at the two heights. Total energy = Sum of PE and KE
That is, mgH = mgh + 0.5mv^2
Here, the initial energy as given is 200J
or 200 = 20mg
or m = 1.01937 Kg
Hence, 200 = 1.01937 g x 10 + KE
KE = 200 - 100 = 100J
Therefore at h = 10m, the KE of the given box is 100 J and also the PE is 100 J
