# Determine the balls initial velocity

## Homework Statement

Question Reads: " A passenger in a hot air balloon throws a ball with an innitial unknown velocity. the ball accelerates at 9.8m/s down for 2.0s. at which time its instantenous velocity is 24m/s [45 below the horizontal]. determine the balls innital velocity "

vf = vi + at

## The Attempt at a Solution

ok, these kinds of problems are very new to me.
i made vf = 24sine45 since we are only discussing the y direction speed.
and vi = visinetheta.

but the answer says 17m/s [10 degress above horizontal]

where did 17 come from along with the angle ? please guide me

## Answers and Replies

How it can gain horizontal velocity component if g only acts in y direction?

So, horizontal speed is contant. The speed at 2 second = speed at 0 second.

Now, you know after two seconds v_y is 24sine45, what it was 2 seconds?

rl.bhat
Homework Helper

It is a projectile motion. Let initial component of velocity along y by viy. Final velocity is given. find vfy. Then use the relevant equation to find viy. Cake care of the signs of the quantities.