A) Energy is conserved because the pendulum is a closed system.

B) Energy is not conserved because the pendulum is not a closed system.

C) Energy is conserved because there is no net force acting on the pendulum.

The correct answer is C. Energy is conserved because there is no net force acting on the pendulum. The only force acting on the pendulum is gravity, and gravity is a conservative force. This means that the total mechanical energy of the pendulum (potential energy + kinetic energy) is constant.

## Other related questions:

### Q: How does a pendulum describe energy conservation?

A: A pendulum is a weight suspended from a pivot point, usually a string or rod, that swings freely back and forth under the influence of gravity. The energy of a pendulum is kinetic energy when the pendulum is in motion and potential energy when the pendulum is at rest. The kinetic energy of a pendulum is given by:

KE = 1/2 mv^2

where m is the mass of the pendulum and v is the velocity of the pendulum. The potential energy of a pendulum is given by:

PE = mgh

where m is the mass of the pendulum, g is the acceleration due to gravity, and h is the height of the pendulum.

The total energy of a pendulum is the sum of the kinetic and potential energies, and is given by:

E = KE + PE

The energy of a pendulum is conserved, meaning that the total energy of the pendulum does not change over time. This is because the kinetic energy is converted to potential energy and vice versa as the pendulum swings back and forth.

### Q: How do swinging pendulum demonstrate the law of conservation of energy?

A: The law of conservation of energy states that energy cannot be created or destroyed, only transformed from one form to another. A swinging pendulum demonstrates this law by converting energy between potential and kinetic energy. As the pendulum swings higher, its potential energy increases. At the peak of the swing, all of the pendulum’s energy is potential energy. As the pendulum falls, this potential energy is converted into kinetic energy. At the bottom of the swing, all of the pendulum’s energy is kinetic energy.

### Q: What type of energy is a pendulum at the bottom of the swing?

A: The pendulum is at its lowest point of potential energy when it is at the bottom of the swing. At this point, the pendulum has kinetic energy, which is the energy of motion.

### Q: What happens to most of the pendulum gravitational potential energy as it reaches the lowest point P?

A: At the lowest point P, the pendulum has the greatest amount of kinetic energy and the least amount of potential energy.