# Height of a building with a Projectile

1. Homework Statement

A ball is launched at an angle of 38° at 16m/s off of the top of a building, the ball finally hits the ground after 45seconds. What is the height of the building? Gravity is normal 9.80m.s squared. The answer to the problem is 9480m.

2. Homework Equations

I just needed a starting point. I wasn't sure really where to go with the problem.

3. The Attempt at a Solution

First i tried to find Vy by 16.0m/s * sin(38°) and got a value of 4.741m/s. I then plugged it into the equation Δy=VyiΔt+1/2gΔtsquared but the answer came out to around 10,000.

Related Introductory Physics Homework Help News on Phys.org
SteamKing
Staff Emeritus
Homework Helper
Why don't you show your complete calculations?

what do you mean?

oh well with the answer i got around 10,000 it was just Y=(16m/s)(45s)+1/2(-9.8)(45)squared which came out to -9202.5

BvU
Homework Helper
Always good to check things.
1. You know sin(30°) = 0.5 so you should expect Vy > 8 m/s !
2. If even that leads to an improbable answer, check that you read the OP correctly. Perhaps it says 4.5 seconds ?

BvU
Homework Helper
Posts crossed. I am a slow typer. Now you use Vo, not Vy. Not that it matters much on a 10000 m scale. But it does on a 100 m scale.

BvU