Answer: 79 J
Step-by-step explanation:
The value of the kinetic energy at the bottom would be equal to the value of potential energy at the top. This comes from the conservation of energy. At the top, the bob of mass just has potential energy due to its position. At the bottom, potential energy converts entirely to kinetic energy due to its motion.
It is given that mass of the bob is, m = 0.18 kg
height from which it is dropped is, h = 45 m
acceleration due to gravity, g = 9.8 m/s²
Thus, K.E. = P.E. = m g h = 0.18 kg× 45 m × 9.8 m/s² = 79 J