# (+)/(-) Acceleration & (+)(-) Velocity

• Does a negative acceleration mean an object is slowing down?
• Does a negative velocity basically mean you are moving at an opposite direction? The sign is just direction?
• – Secret Jan 27 '16 at 8:35
• Note that yes/no questions e not a good fit for this site because the answers (yes or no) are too short to be valid answers. – Kyle Kanos Jan 27 '16 at 11:01

Think of a position axis $x$ starting at zero, positive to the right and negative to the left.
It is like a number line.

A positive velocity means that the value of $x$ is increasing eg going from $x=+3$ to $x=+5$ or $x=-7$ to $x=-4$ or $x = -3$ to $x=+4$.
A negative velocity means that the value of $x$ is decreasing eg going from $x=-3$ to $x=-5$ or $x=+7$ to $x=+4$ or $x = +3$ to $x=-4$.

A positive acceleration mean that a velocity is becoming more positive (or less negative) eg going from $v=+3$ m/s to $v=+5$ m/s or $v=-7$ m/s to $v=-4$ m/s or $v = -3$ m/s to $v=+4$ m/s.

A negative acceleration mean that a velocity is becoming more negative (or less positive) eg going from $v =-3$ m/s to $v =-5$ m/s or $v =+7$ m/s to $v =+4$ m/s or $v = +3$ m/s to $v =-4$ m/s.

well you have given answer in your own question! Velocity and acceleration are both vector quantities, meaning they have magnitude and 'direction'. The sign (+/-) will depend on the direction. To simplify, let me give you an easy example.. Case 1: An object is moving down from the top of a mountain. The acceleration (in this case 'g') will act in the direction of motion, hence called as 'positive acceleration'. Case 2: Same object is moving up. The acceleration (g) will act in the opposite direction of motion, hence called as 'negative acceleration'.

The same logic is behind negative velocity.