acceleration?

Question

If someone says that a negative acceleration always means that the moving object is decelerating. is this statement true and why?

Answer 1

Yes, negative acceleration means there is a decreasing speed.

It depends on weather or not you are using vectors. If you are measuring your displacement and velocity, negative acceleration can mean movemet in the opposite direction.

If you are using speed, then acceleration in any direction will be positive.

Answer 2

The meaning of deceleration in physics is vague. Let's say it this way. A negative acceleration means the object is accelerating in the negative direction.

If the object has a positive velocity and a negative acceleration, the magnitude of its velocity is decreasing (slowing towards a stop).

If the object has a negative velocity and a negative acceleration, the magnitude of its velocity is increasing (becoming even more negative).

Answer 3

Acceleration IS a vector. If an object is moving in the negative direction and it also has negative acceleration that means the object's velocity vector and its acceleration vector point in the SAME direction. Thus the object is speeding up (accelerating) in the negative direction.

General rule: if the acceleration vector and the velocity vector point is the same direction, the object is speeding up.
If the acceleration vector and the velocity vector point in opposite directions the object is slowing down.

Physics is Phun

Answer 4

it's not always true.
acceleration is an vector and vectors have directions

going to the left or downward is a negative acceleration but the object can still speeding up.

Answer 5

no acceleration is also called negative when we consider vertical direstion motion, in this the acceleration acting downwards is also called negative also it is called acceleration due to gravity . it is denoted by 'g' and its value is g= -9.8 m/s^2

Answer 6

yes in a way, but it also means going back(rewind).