Velocity and Acceleration question. See image.

Question

fellowroot · Answer

My question is about part B. Is it slowing down or speeding up? Some of my classmates said that if both your velocity and acceleration are negative then its actually speeding up. I disagree and say that the only function you need to look at is the acceleration one. If at t=4 the acceleration is negative then it should be slowing down. Please help. thanks.

ipwnbunnies · Answer

I believe it's only one way due to the technicality of the physics terms. I'm not too sure.
But, I disagree with you.
If the velocity and acceleration are BOTH negative, the object is technically speeding up. Speed is just the magnitude to velocity, and doesn't necessarily depend on position or direction. My opinion.

fellowroot · Answer

So could you possibly explain why if both are negative then its actually speeding up.

ipwnbunnies · Answer

I thought I explained it. The magnitude of rate of change of your displacement is increasing as you 'speed up' going backwards.  So, I would say you're increasing your speed, but decreasing your velocity. Velocity is a vector quantity, so it's defined with a magnitude (which is speed) and a direction.