Posted by Anna on .
Someone posted the question below, stating that they knew the answer to part A but needed help with part B. Well even with the answer for A, I can't figure it out! Can you take a step back from the question below to show me the steps for solving part A? I've been working on this for 2 days!
thanks!
This question was submitted by Sam on Friday, September 26, 2008 at 8:59pm. The subject of this question is Physics.

a) A cannonball is fired horizontally from the top of a cliff. The cannon is at height H = 100 m above ground level, and the ball is fired with initial horizontal speed v_0. Assume acceleration due to gravity to be g = 9.80 m/s^2. Assume that the cannon is fired at time t = 0 and that the cannonball hits the ground at time tg. What is the y position of the cannonball at the time tg/2?
I got 75m and I know that one is right.
I need help with part b
Given that the projectile lands at a distance = 110 from the cliff, as shown in the figure, find the initial speed of the projectile, .

Physics 
bobpursley,
If you know tg, you know the time it was in the air.
Horizontal distance=initialhorizontal veloicty*tg
solve for initialhorizonalveloicty vo