Answer:
The sign of acceleration is positive.
Explanation:
Consider the provided information.
It is given that A student drops a penny from the top of a tower and decides that she will establish a coordinate system in which the direction of the penny's motion is positive.
Here the direction of the velocity is positive, and the velocity is increasing.
Acceleration is defined as the rate at which an object changes its velocity.
Since velocity is positive therefore the acceleration is also positive.
Hence, the sign of acceleration is positive.