Another simple physics question

We are only dealing with what happens to the ball/object after it leaves the hand. Thanks.

 

In case people did not see it on the first page:
Deceleration means negative acceleration.
Acceleration means positive acceleration (the vector points the other way).

 

I did try to clarify it. Yes, the wording could have been better. You are of course correct.

 

OK answer time. The only force acting on the ball is gravitational acceleration. It is always positive, downwards. So, relative to the boy, the ball is always accelerating. The acceleration is always positive.

I could have worded it better. Those who said it is decelerating and then accelerating are on the right track. But after I clarified twice that acceleration means positive acceleration and deceleration means negative acceleration, the only right answer was A.

The key here was that it was accelerating positively with respect to the ground while it was going up. Since it's velocity was negative, the positive acceleration downward caused the negative velocity downward (positive upward) to decrease. Once it decreased to zero, the ball reached its peak and started to accelerate due to the only force acting on it. This was gravity pulling it downward. So it accelerated downward (positively towards the earth). So its speed kept increasing and it went down faster and faster till it hit the earth.

The acceleration was positive at all times with respect to the boy, who is on the earth.

 

Someone mentioned coriolis forces in this thread.

Here is a great, great explanation. I wish someone had explained it to me this well in school. I had to try and understand it from a physics textbook, which wasn't very good.

http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/crls.rxml

 

First of all, you choose to misinterpret the question and look at boundary cases. If you were to interpret it the way you have, there would be several stages:
acceleration in the hands of the thrower
deceleration going up
acceleration coming down
deceleration on impact
and numerous smaller cycles as it bounced.
Clearly you have to be delusional to interpret the question like this.

Secondly, if we are talking about acceleration per se, nope, it does not decelerate when it hits the earth. It's speed goes to zero instantly. There is never a period where it "slows down. You can also say, tt keeps accelerating but the acceleration is countered by the hard surface of the earth not giving way so all it can do is press down with its weight. This is not enough to bore a hole through the surface and keep on accelerating due to the gravitational acceleration.

The ball is always accelerating due to the force of gravity acting on it. Even when it is at rest. Just like you and every other object on this earth. We are of course neglecting all the other forces acting on objects on each, wind, magnetic fields, Ferrari seats pushing you forward very hard, and so on. On earth, gravitational acceleration is ALWAYS constant and positive in the down direction.

Unlike your question about the wiring, this is not a trick question. It just requires an understanding of physics principles.

I also clarified it twice.

Decelaration is negative acceleration.
Acceleration is positive acceleration.

 

Ash, see my clarifications above. You are of course correct.