A man stands on the roof of a building of height 16.3m and throws a rock with a velocity of magnitude 31.6m/s at an angle of 28.1 degrees above the horizontal. You can ignore air resistance(adsbygoogle = window.adsbygoogle || []).push({});

A.) Calculate the maximum height above the roof reached by the rock. Take free fall acceleration to be 9.80 m/s^2.

ok first i found vectors x and y at 28.1 degrees

cos(28)*31.6 = vector x

sin(28)*31.6 = vector y

x = 27.8752

y= 14.883

using this formula:

x(t) = x(0) + v(0)t + 1/2at^2

x(t) = 16.3 + (31.6m/s)t + 1/2(-9.8)t^2 <--- is that right how i set it up? is a a negative or positive number? and will there be two times? i know im doing something wrong, i just dont know what...if i solve for t now, there will be two times, which i dont know what to do with it.

B.) Calculate the magnitude of the velocity of the rock just before it strikes the ground. Take free fall acceleration to be 9.80 m/s^2

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Projectile motion of a rock

**Physics Forums | Science Articles, Homework Help, Discussion**