# Free-Fall Kinematics equation- how to find acceleration when just given initial speed

## Homework Statement

A ball is thrown downward with an initial speed if 20 m/s on earth.
What is the acceleration of the ball?

## Homework Equations

vf=a (change in time)t + vi

## The Attempt at a Solution

well you have to find the velocity of then find acceleration. and acceleration is m/s^2
on my notes it says that the horizontal acceleration is 0 m/s/s since its being thrown downward, (in a horizontal direction) thats what is getting me confused.

Acceleration is a vector quantity - i.e. it has a direction. So as the ball is being thrown downwards and the force (do you know what it is) is also acting downwards there isn't going to be a horizontal acceleration but there will be a vertical one :)

Does this help?

Last edited:
Doc Al
Mentor

What is the acceleration of the ball?
Hint: No calculation needed here. The acceleration of any object in freefall is the same. (What's the acceleration due to gravity?)