John's weight on the ground is 145 lb. He enters an elevator and stands on a scale. During its upward motion, the elevator accelerates from zero to [tex]2 \, \text{m/s}^2[/tex].

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When an elevator accelerates upward, the scale reading is greater than the person's weight. When it accelerates downward, the scale reading is less than the person's weight. If the elevator is in free fall, the scale reading is zero and the person appears weightless.

Explanation:

When an elevator accelerates upward, the scale reading is greater than the person's weight. This is because the scale is pushing up on the person with a force greater than the person's weight to accelerate them upward. As the acceleration of the elevator increases, the scale reading also increases. When the elevator has a constant velocity or is stationary, the scale reading is equal to the person's weight.

Similarly, when an elevator accelerates downward, the scale reading is less than the person's weight. If the elevator reaches a constant downward velocity, the scale reading becomes equal to the person's weight again. If the elevator is in free fall and accelerating downward at the acceleration due to gravity(g), then the scale reading is zero and the person appears to be weightless.

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