As the pendulum moves from point 1 to point 3, what happens to its mechanical energy?

The mechanical energy of a pendulum is the sum of its kinetic energy and potential energy.

1. At point 1, the pendulum is at its highest point in the swing, so it has maximum potential energy and zero kinetic energy.

2. As the pendulum swings down towards point 2 (the lowest point), it loses potential energy but gains kinetic energy. The total mechanical energy remains constant, assuming no air resistance or friction.

3. As the pendulum continues to swing up towards point 3, it starts to lose kinetic energy and gain potential energy.

So, as the pendulum moves from point 1 to point 3, its potential energy decreases and then increases, while its kinetic energy increases and then decreases. The total mechanical energy remains constant, assuming no energy is lost to air resistance or friction.