# What does an applied force on an already accelerating object do?

I'm a big beginner having only taken Grade 11 high-school physics.

Imagine this situation: an object is accelerating north, and while it's accelerating, it's 'hit' by a northward force.

To me it would make sense that the acceleration of the object would increase - something like this:

aNew = aOld + (f/m)


I got the (f/m) from f=ma.

But then think of gravity - while an object is accelerating downward at 9.8m/s2, it has the force of gravity pulling it too. So then, based on my previous logic, it's acceleration would constantly be increasing!

aNew = aOld + (fGravity/mass)


And I know that you don't increase your acceleration while you fall, so now I'm confused.

In a nutshell: What exactly are the rules for how an already accelerating object reacts to forces? Am I wrong that your acceleration would increase?

EDIT: I realized I've made a big mistake; I never knew that the acceleration drops to 0 the second the net force is 0. This makes sense now.

• No need to say you made a "big mistake". You had a misunderstanding and it got cleared up. That is what this site is for. Glad we could help you this time! Come back often... – Floris Jun 10 '14 at 1:57