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Answer:
<em>Answer: - , + </em>
Explanation:
<u>Velocity and Acceleration </u>
In general terms, velocity and acceleration in the plane are both vectors with two components. They don't have 'sign' but magnitude and direction. If we know motion is restricted to a simple line, then we can define the positive and negative references.
In vertical motion, the positive reference is commonly pointed upwards, but if we chose the opposite way, the results shouldn't change in magnitude, just their signs. Let's choose like proposed, the positive direction upwards.
Since the elevator was moving downwards, its velocity is negative. When the button is pushed, it continues to move downwards, but slower. Its velocity is still negative.
The acceleration has the same sign as the velocity if it tends to increase the magnitude of the object, and is negative in the opposite case. Let's look at the formula
In this case, because the elevator will eventually stop, and
is negative. It means the acceleration is
It results in a positive value
Note: If we chose the opposite references, then the answer would be: +,-