Question

The bob of a pendulum has 600 J of kinetic energy at the bottom of its swing. As the bob rises to a height of 4 m above the bottom, it gains 400 J of potential energy. How much kinetic energy does it have at this point?

200 J

300 J

400 J

1000 J

Answer 1

The K.E of the pendulum is, K.E = 200 J

Step-by-step explanation:

Given data,

The kinetic energy of the bob of the pendulum at the bottom, K.E = 600 J

The potential energy at the height 4 m, P.E = 400 J

According to the conservation of energy, the total energy of the mechanical system should be conserved.

At the bottom of the swing, the entire mechanical energy of the pendulum is purely kinetic. Therefore the total energy

E = P.E + K.E

= 0 + 600 J

= 600 J

Therefore, the total energy of the system, E = 600 J

At height 4 m, the total energy of the system remains the same.

Therefore,

600 J = 400 J + K.E

K. E = 600 J - 400 J

= 200 J

Hence, the K.E of the pendulum is, K.E = 200 J