How High Was the Ball Thrown From the Building?

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Homework Help Overview

The problem involves a ball being thrown from a building with an initial velocity at an angle below the horizontal. The objective is to determine the height from which the ball was thrown, given the time it takes to hit the ground.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the initial velocity's components, particularly the need to separate horizontal and vertical components due to the angle of projection. There is also mention of utilizing projectile motion formulas for a clearer approach.

Discussion Status

Some participants have provided guidance on correctly interpreting the initial conditions of the problem, suggesting a focus on the vertical component of the initial velocity. There is acknowledgment of the original poster's misunderstanding regarding the velocity's direction.

Contextual Notes

The original poster's calculations appear to be based on an incorrect assumption about the initial velocity's direction, which has been pointed out by other participants. There is a reference to external resources for projectile motion formulas, indicating a potential avenue for further exploration.

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Homework Statement


A ball is tossed from an upper-story window of a building. The ball is given an initial velocity of 8.70 m/s at an angle of 22.0° below the horizontal. It strikes the ground 5.00 s later.
Find the height from which the ball was thrown.


The Attempt at a Solution


i found final Velocity first: -8.70 + (-9.80)(5) and i got -57.7
then i used this formula yf-yi = 1/2(Vy+Vi)t 1/2(-57.7 + -8.70)5
to get 166 for the height, but it is wrong.
 
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The problem is that you took the entire initial velocity to be in the vertical direction, but the ball was thrown at an angle so in reality, part of that velocty is in the horizontal direction. You need to use the initial angle given and solve for the initial velocty in the y direction, and that's the velocity that will change due to gravity.
 
thank you, that helped
 
Try using some of the extra forumlas given for projectile motion, you can find them on wikipedia ect. they help a lot, plus they're easier to use then 2D motion
 

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