You are standing on a scale in an elevator. suddenly you notice your weight decreases. what do you conclude? a. the elevator is accelerating downwards. b. the elevator is accelerating upwards. c. the elevator is moving at a constant velocity upwards. d. your diet is working. e. the elevator is moving at a constant velocity downwards.

The elevator is accelerating downwards.

Explanation:

When an elevator accelerating downward it moves together with the person inside and the weight of the person does not change, but if the person is standing on a scale the contact force between the person and the scale is reduced.  The scale therefore has to push upward with less force on the person to support the person's weight. Therefore the Normal Force is smaller, so the reading on the scale becomes less than the true weight.

b.transmitters send radio waves, and receivers capture radio waves.

the motion of a pendulum is a classic example of mechanical energy conservation. a pendulum consists of a mass (known as a bob ) attached by a string to a pivot point. as the pendulum moves it sweeps out a circular arc, moving back and forth in a periodic fashion.