The elevator designers chose the magnitude of the maximum positive acceleration

Question

The elevator designers chose the magnitude of the maximum positive acceleration when ascending to be significantly greater than the magnitude of the maximum negative acceleration (deceleration) when descending; however, both magnitudes of acceleration are significantly smaller than the magnitude of the acceleration due to gravity.

A) Hypothesize the rational of the elevator designers to choose the magnitude of the maximum positive acceleration when ascending to be significantly greater than the magnitude of the maximum negative acceleration (deceleration) when descending.

B)Hypothesize the rational of the elevator designers to choose the magnitude of the maximum positive acceleration when ascending and the magnitude of the maximum negative acceleration (deceleration) when descending to be significantly less than the magnitude of the acceleration due to gravity.

Explanation / Answer

A) magnitude of the maximum positive acceleration when ascending is generally greater than that when descending because when an elevator assends the pseudo force that acts on a person inside is in complement with the force of gravity. This increases the normal reaction between the person and floor and will cause the person to feel heavy. The descending acceleration causes pseudo forces in direction opposite to gravity and if it is large, the person may loose contact from floor. Also larger deacceleration force needs to be generated while stopping since gravity is not contributing to it. For these reasons, magnitude of the maximum positive acceleration when ascending is generally greater .

B) Again, if the acceleration is of the order of g, then during descent ground contact can be lost and the person may start to float or even worse hit the ceiling and hurt himself/herself. During ascent, it will increase the load on muscular system of the person and may even cause nausea or blood pressure related issue.

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