# External unbalanced force

1. Sep 25, 2015

### Karan Punjabi

Guys I'm a student studying in FYJC sci. I like to get things in deep so i want to just ask a question... I don't know this question can be silly or not but i want to know that If on an object I acted a certain force for a time then the object will accelerate for that time i mean at that instant only for which force is acting or after it... I think this can be silly but please help me

2. Sep 25, 2015

### Geofleur

An object will accelerate only while a nonzero net force is being applied to it. So, for example, imagine that you are throwing a baseball. While the ball is in contact with your hand, there are two forces on the ball: the one you are exerting in order to speed the ball up and also the force of gravity downward (the ball has a weight). Once the ball leaves your hand, you are not exerting a force on it anymore. Gravity will continue to act on the ball and air resistance will act as the ball flies through the air.

Short answer: An object only accelerates while a force is being applied.

3. Sep 25, 2015

### Karan Punjabi

I understand this but we interpret like the ball is accelerating after the throw but actually it accelerates till we throw it right?

4. Sep 25, 2015

### DocZaius

Neither. It accelerates during the throw. The hand pushes the ball during the throw. Surely you're asking about something more subtle than this and we're missing it?

5. Sep 25, 2015

### Geofleur

Let's ignore gravity and air resistance. We'll suppose you are throwing the ball in outer space. The ball will accelerate only while it is in contact with your hand. As soon as it leaves your hand, it will fly off in a straight line at a constant speed.

6. Sep 25, 2015

### Karan Punjabi

Yeah that's what i was confused about..... It till will accelerate till the ball is in my hand. Thank you both to solve my problems