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April 30, 2016

# Homework Help: Physics

Posted by Min on Tuesday, November 21, 2006 at 8:54pm.

A bullet is fired horizontally from the roof of a building 100 meters tall with a speed of 850 m/s. Neglecting air resistance, how far will the bullet drop in 3 seconds?

1 29.4 m
2 44.1 m
3 100 m
4 2550 m

Answer should be choice 2) 44.1m

BUT I DON'T GET IT!

if i remember the formula correctly as:
x = (-9.8/2)t^2 + vt + x0
x = (-9.8/2)(3^2)
x = 44.1 m

You split up this problem into horizontal and vertical components like below:
a = acceleration
v = velocity
x = distance
x0 = starting distance (usually 0)
t = time
Vertical:
a = -9.8m/s^2
v = none (they said that the bullet was shot horizontally so vertically, it would be like the velocity at the peak of a free-fall.
x = 100 m
x0 = 0 m (this is like the starting point of the fall so technbically 0)
Horizontal:
a = none (gravity doesn't move sideways and there's no given acceleration)
v = 850m/s
x = (not given)
x0 = (not given)
:)

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