Answer to Question #145293 in Physics for Dipu

Question

Explain how the mechanical energy of the objects change. Is there external work done on the system? If so, by what forces? Is the work positive or negative? (1p/case)

A person climbs up a ladder.
A pendulum in a clock tower swings back and forth.
A bicyclist slows its speed on a horizontal road. Describe energy changes for the bicycle.
An archer shoots an arrow in an arc. Describe energy changes for the arrow.

Answer 1

A person climbs up a ladder: potential energy increases since the climber performs work.

A pendulum in a clock tower swings back and forth: the sum of potential and kinetic energy is constant all the time. At the highest point the potential energy is the highest, the kinetic energy is the lowest. At the lowest point the potential energy is the lowest and kinetic energy is the highest.

A bicyclist slows its speed on a horizontal road: force of friction performs work. Kinetic energy is waster to overcome friction.

An archer shoots an arrow in an arc: elastic potential energy converts into kinetic energy.