a rock.is thrown upwards from the roof of an 15.0m high building at 30.0m/s at a

Question

a rock.is thrown upwards from the roof of an 15.0m high building at 30.0m/s at an angle of 33 degree. find the speed of the rock when it strikes the ground Vox=25.2 m/s Voy=16.3 m/s a rock.is thrown upwards from the roof of an 15.0m high building at 30.0m/s at an angle of 33 degree. find the speed of the rock when it strikes the ground Vox=25.2 m/s Voy=16.3 m/s a rock.is thrown upwards from the roof of an 15.0m high building at 30.0m/s at an angle of 33 degree. find the speed of the rock when it strikes the ground Vox=25.2 m/s Voy=16.3 m/s

Explanation / Answer

Given
v=30 m/s
=33°
h=15m
g=9.8 m/s²

Resolve velocity into horizontal (vx) ad vertical (vy) components,
vy=v*sin()= 16.34 m/s
vx=v*cos()= 25.16 m/s

Find time t to reach ground h m below:
y=vy*t+(1/2)at²
-15=16.34t-4.9t²
=>
4.9t²-16.34t-15=0
t=4.084 s (reject negative root)

Calculate horizontal distance
x=vx*t
= 25.16*4.084
= 102.8 m (approx.)

then speed=102.8/4.084=25.17 m/s

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