The electric potential energy of an object at point A is known to be 60 J. If it is released from rest at A, it gains 20 J of kinetic energy as it moves to point B. What is its potential energy at B?
PE2 = PE1 - KE = 60 - 20 = 40 J.
To determine the potential energy at point B, we need to consider the conservation of energy. The total mechanical energy of the object is conserved, which means the sum of its potential energy and kinetic energy remains constant.
Given that the object gains 20 J of kinetic energy as it moves from point A to point B, we can deduce that its potential energy at point B decreases by the same amount. This is because the gain in kinetic energy comes from the loss of potential energy.
Therefore, to find the potential energy at point B, we subtract the gain in kinetic energy (20 J) from the initial potential energy at point A (60 J):
Potential energy at B = Potential energy at A - Gain in kinetic energy
Potential energy at B = 60 J - 20 J
Potential energy at B = 40 J
Hence, the potential energy at point B is 40 J.