Okay so I am learning the basic physics stuff, projectile motion, relative motion, 1-D problems 2-D problems, and i'm really stumped.
I should be looking for 2 - 3 givens in each question...
if someone could help me via AIM or something that would be awesome..

Sample question:

A lovesick lad wants to throw a bag of candy and love notes into the open window of his girlfriends bedroom 10.0m above. Assuming it just reaches the window, he throws the love gifts at 60.0 degrees to the ground:

A) At what velocity should he throw the bag?

B ) How far from the house is he standing when he throws the bag?


I have a few i'm stuck on, please help :s

This post was edited by Dunner on Mar 6 2012 06:04pm

For B its just basic geometry. You have a 30 60 90 triangle and one side (10m high) find the base.

Pretty easy.

Projectile motion follows S = (1/2)at^2 +v_0t + s_0
s_0 = 0 in this game, as we're dealing with standing on the ground throwing up.
We'd like our maximum V = at + v_0 to be when the bag reaches the window at height 10.
At this time we have 0 = at + v_0 and thus v_0 = -at

Thus, we're looking at:

10 = 1/2(-9.8)t^2 +v_0t

simplifying and moving to one side gives us

-4.9t^2 + v_0t - 10 = 0

Substituting for v_0 we get:

-4.9t^2 - 9.8t -10 = 0

Use the quadratic formula to determine the roots here.

That gives you a time,

This will give you a time, and then plug this time into our equation v=-9.8t to get the velocity

This is the velocity in the upward direction. To figure out then the overall velocity use your 30-60-90 sine/cosine geometry.

We want the hypotenuse, and now we have the opposite. Thus, we do sin(60)=v_0/V
V = v_0/sin(60)

To determine the adjacent (horizontal) velocity just use tan instead