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February 13, 2016

# Homework Help: Physics

Posted by Tammy on Wednesday, September 26, 2007 at 1:27pm.

A projectile is shot horizontally at 30m/s from the roof of a building 100m tall. Use g=10m/s^2. Choose + vertical direction to be pwards.
a) determine the time necessary fot the projectile to reach the ground below
b) determine the horizontal distance from the base of teh building that the projectile lands
c) determine the horizontal and vertical components of the velocity just before the projectile hits the ground
d) determine the magnitude of the total velocity just before the projectile hits the ground.

a)would I use y=y_0 +v_0t +1/2 at^2
100=0+0+1/2(-10)t^2 and solve for t? when i did i got 4.47s
b) would i use x=x_0+v_xt
=0+30*4.47
=134.1m
c)for the horizontal componet i believe i use v=v_0 +at and for the vertical: x=x_0+vt
d) v_total =sqrt(vx^2 +vy^2)

Are these equations I came up with correct to solve this problem?
• Physics - bobpursley, Wednesday, September 26, 2007 at 1:53pm

a) right equation.
b) right
c) NO. Horizontal velocity remains the same as initial (30m/s). The vertical velocity is -g*timeinair.
d)Right formula.