Question

The pendulum of a clock swings through its stable equilibrium rather than stopping at that equilibrium. To

stop abruptly at the equilibrium point, the pendulum would have to get rid of what conserved quantity or
quantities?
a) Energy, but not momentum.
b) Energy and momentum.
c) Momentum, but not energy.
d) Acceleration and velocity."

Answer 1

The pendulum must get rid of both energy and momentum to stop abruptly at its equilibrium point. Momentum is conserved in a closed system with no external forces, and mechanical energy is conserved in the absence of non-conservative forces.

Step-by-step explanation:

The pendulum of a clock swings through its stable equilibrium because it possesses both kinetic energy and momentum. When the pendulum swings through the equilibrium point, it has the greatest speed and hence the maximum kinetic energy and momentum in the absence of external forces acting upon it. For the pendulum to stop abruptly at the equilibrium point, it would have to get rid of both these conserved quantities. This means that the correct answer is b) Energy and momentum. Momentum is conserved in a closed system where no external forces are acting upon it. Similarly, in the absence of non-conservative forces, such as friction, mechanical energy (which includes kinetic energy) is also conserved. Thus, the conservation of mechanical energy allows for the pendulum's motion between potential and kinetic energy as it swings.