# Acceleration of a ball thrown upwards.

1. Oct 11, 2008

### kbncp

1. The problem statement, all variables and given/known data
A ball is thrown up the top of the tower. At each of the following instants is the ball's acceleration larger than g, equal to g, or -g (assume up is positive, g=9.8m/s2)
a) Just after leaving your hand?
b) When the ball is at its highest point?
c) Just before hitting the ground?

2. Relevant equations

3. The attempt at a solution
a) -g
b) -g
c) g

2. Oct 11, 2008

### borgwal

Your answers are not all correct: but you should say more about how you arrived at your answers. If they are random guesses then you should try harder.

In any case, I suppose air friction is neglected here, otherwise the correct answer is not always among the 3 choices!

3. Oct 11, 2008

### kbncp

well the first two answers.. since the ball is moving up.. it is eventually going to reach a velocity of 0, so it slows down.. so acceleration is -g... And when it is moving down... the velocity gets faster and faster.. so i would assume that the acceleration would be g

4. Oct 12, 2008

### borgwal

Maybe you're confusing speed and velocity: it's not just about "speeding up" or "slowing down," [which refer to speed, really] it's the direction of the change in velocity which is important.