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Find the height from which the ball was thrown

1. Homework Statement
A ball is tossed from an upper story window of a building. The ball is given an initial velocity of 8.0m/s at an angle of 20.0 below the horizontal. It strikes the ground 3.00s later.

a) How far horizontally from the base of the building does the ball strike the ground?
b) Find the height from which the ball was thrown
c)How long does it take the ball to reach a point 10.0 below the landing?


2. Homework Equations
for a. the equation is R=vxit=vicostheta)*2t
for b. h=v^2sin^2thetai/2*g
for c. I think its Rmax


3. The Attempt at a Solution
ive plugged in the values to the equations but i still dont get the correct answer
 

Answers and Replies

learningphysics
Homework Helper
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Part a) should be straightforward. What is the initial horizontal velocity? Does the horizontal velocity change at all?

you're also given the time... so you can calculate the horizontal displacement.
 
learningphysics
Homework Helper
4,099
5
innightmare;1432888 [b said:
2. Homework Equations [/b]
for a. the equation is R=vxit=vicostheta)*2t
Why 2t?

for b. h=v^2sin^2thetai/2*g
They're not asking for the height the object reaches (which you won't get from this equation anyway... this equation only works when the initial height is 0)... they're asking for the height from which it is thrown.

Don't try to use those formulas... stick to the basic kinematics formulas. Keep it simple.
 

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