Question

When an object is dropped from the top of a tall cliff, your teacher tells you to use -10 m/s2 for the approximate acceleration due to gravity. What sign should the displacement of the object have and why? A) The displacement should be positive, because it only moves in one direction. B) The displacement should be positive, because this choice would make calculations easier Eliminate C) The displacement should be negative, because the negative represent a downward direction. D) The displacement should be positive, because you can never have less than zero displacement.

Answer 1

The displacement should be a negative value.  since your zero point is where you dropped it.  The answer is C

Answer 2

Answer:

C) The displacement should be negative, because the negative represent a downward direction.

Explanation:

As we know that acceleration due to gravity is having magnitude 10 m/s/s and its direction is always downwards.

Now in order to solve for displacement we will use the equation of kinematics

$\Delta y = v_i t + \frac{1}{2}at^2$

now here since ball is dropped so we will say

$v_i = 0$

now we have

$\Delta y = \frac{1}{2}at^2$

so here direction of acceleration and displacement must be same as per the equation.

so displacement must be negative as it is downwards due to the downwards acceleration.