Free fall question

1. Oct 23, 2008

physics_geek

1. The problem statement, all variables and given/known data
A ball is tossed from an upper-story window of a building. The ball is given an initial velocity of 8.20 m/s at an angle of 15.0° below the horizontal. It strikes the ground 3.00 s later.
(a) How far horizontally from the base of the building does the ball strike the ground?
4.90wrong check mark m
(b) Find the height from which the ball was thrown.
wrong check mark m
(c) How long does it take the ball to reach a point 10.0 m below the level of launching?

2. Relevant equations
i think the equations are r= v^2(sin2theta)/g
h= v^2(sintheta)2/2g

3. The attempt at a solution
i tried pluggin in the values to get how far it travelled and the height..but im getting it wrong

any help would be appreciated

2. Oct 23, 2008

mgb_phys

Work out the velocity component downward.
Then it's just the normal moving object equations except the initial velocity isn't zero.

3. Oct 23, 2008

physics_geek

im not sure wat you mean by that

make the velocity -8.2?
im so confused

4. Oct 23, 2008

cristo

Staff Emeritus
You need to resolve the velocity vector into horizontal and vertical components. Then, what mgb is saying, is you consider the vertical component.

5. Oct 23, 2008

physics_geek

o ok into two different components

so they give me 8.2 m/s
thats my resultant vector rite?

so i just do 8.2(cos15) ??

6. Oct 23, 2008

mgb_phys

Draw a diagram (triangle) - it should be obvious how much of the diagonal speed goes horizontally and how much vertically.

7. Oct 23, 2008

physics_geek

alrite cool
thanks a lot guys