Question

Which of shakina's statements regarding acceleration and velocity is false? "when the acceleration is negative, the velocity can be either negative or positive." "when the acceleration is negative, the velocity must also be negative."?

Answer 1

Let's start by imagining a rock being thrown to the air.
Let's say that going up is the positive direction and so, going down is the negative.
The acceleration is pointing down (because of gravity) so it's always negative. While the rock is going up, it's velocity/speed is positive, but the acceleration is negative.
While the rock is going down, both acceleration and speed are negative.
This shows that the first statemente is true, but the second is false.
You can also think that if you define going DOWN as the POSITIVE direction, you can have both positive acceleration and speed, or positive acceleration and negative speed.