Question

true or false
a person will feel more than their normal weight whenever they are moving upward.
if false, explain why the statement is false.

true or false
a fast - moving (speed) person will always feel heavier than normal.
if false, explain why the statement is false.

b. try this at home (or somewhere there is an elevator). you do not need to perform this for your report. take your scales and observe them as you ride up and down on an elevator. can you determine the elevators accelerations?

Explanation:

First statement

Step1: Analyze upward - motion condition

A person feels more than their normal weight when moving upward only if the elevator (or upward - moving object) is accelerating upward. If it is moving upward at a constant velocity, the normal force equals the person's weight and they feel normal. So the statement "A person will feel more than their normal weight whenever they are moving upward" is false.

Second statement

Step1: Analyze speed - weight relationship

Weight is related to the normal force acting on a person. Just moving fast (constant speed) does not change the normal force. A person feels heavier when there is an upward acceleration. So the statement "A fast - moving (speed) person will always feel heavier than normal" is false.

Part b

Step1: Recall Newton's second law

According to Newton's second law $F = ma$, where $F$ is the net force, $m$ is the mass and $a$ is the acceleration. When on a scale in an elevator, the normal force $N$ measured by the scale is related to the weight $mg$ and acceleration $a$ by $N - mg=ma$ (taking upward as positive). So $a=\frac{N - mg}{m}=\frac{N}{m}-g$. By observing the scale reading $N$ (which gives the normal force) and knowing one's mass $m$ and $g$, we can determine the acceleration of the elevator.

Answer:

• First statement: False. A person feels heavier than normal when moving upward only if there is an upward acceleration, not just when moving upward.
• Second statement: False. Moving fast (constant speed) does not make a person feel heavier; an upward acceleration is required.
• Part b: Yes, by using Newton's second law $a=\frac{N - mg}{m}$, where $N$ is the scale - reading (normal force), $m$ is the person's mass and $g$ is the acceleration due to gravity.