# Acceleration of a body( negative velocity and speeding up)

1. Nov 19, 2015

### Icy98

1. The problem statement, all variables and given/known data
What is the acceleration of a body which is moving in opposite direction(assuming negative velocity) and is speeding up?

2. Relevant equations
acceleration=the rate of which an object changes its velocity

3. The attempt at a solution
In my opinion, an object moves with a negative velocity and is speeding up can be regard as having negative acceleration. This is what I learn from the notes provided on Physics Classroom. Is this correct?

2. Nov 19, 2015

### PeroK

Yes. In this scenario velocity and acceleration are both negative.

If the acceleration were positive, the object would slow down, stop instantaneously, then move with increasingly speed in the positive direction.

3. Nov 19, 2015

### Icy98

So if the object is moving in opposite direction but it is slowing down, hence it has positive acceleration?

4. Nov 19, 2015

### PeroK

Best to say "negative" direction. Yes. That would be positive acceleration.

This is important because when you have problems involving gravity (or any force), you can take the positive direction to be upwards. In that case gravity is a negative acceleration. And, sometimes, you take downwards to be positive and gravity is a positive acceleration. So, you need to understand both cases.

5. Nov 19, 2015

### Icy98

Alright. Thank you very much