The diagram shows a swinging pendulum.

which best explains what happens to the motion of the pendulum?

a. the mechanical energy transforms to thermal energy as the pendulum slows and eventually stops moving.

b. the mechanical energy disappears as the pendulum slows and eventually stops moving.

c. the pendulum will continue moving at the same speed until someone stops it because energy cannot be destroyed.

d. the pendulum will slow down but will never stop moving because energy cannot be destroyed.

The correct answer is

A. The mechanical energy transforms to thermal energy as the pendulum slows and eventually stops moving.

In fact, we must keep in mind the presence of the air, which causes some resistance to the motion of the pendulum. As the pendulum moves through the air, part of its mechanical energy is transferred to the molecules of air because of the friction of this molecules with the surface of the pendulum. As a result, the pendulum slows down, and eventually stops. The initial energy of the pendulum has been converted into thermal energy of the molecules of air, which move faster now.

answer: the exterior temperature of commercial jet planes as they leave the stratosphere and return to the ground increases steadily.

explanation:

the lower most layer of atmosphere is troposphere which extends from 0 to 12 km above the surface of the earth. the temperature initially decreases as distance is increased from the earth's surface. commercial jets fly in lower part of the stratosphere. the stratosphere extends upto 50 km. the temperature in stratosphere starts rising again due to presence of ozone which traps the uv rays.

thus, when the planes leave the stratosphere and return to the ground, the exterior temperature increases steadily.