Posted by Physics on Friday, January 29, 2010 at 10:30pm.
a man stand on a 100 m cliff and throws a rock with speed of 40ms at 42degrees above horizontal.
what time before rock hits ground.
the horizontal distance the rock traveled from base of cliff.?
my answer is 4.08 sec before rock hits ground
81.6 m distance traveled from base of cliff

Gweedo8  drwls, Saturday, January 30, 2010 at 1:05am
The height of the rock above the base of the cliff is:
Y = 100 + 40 sin 42 t  4.905 t^2
= 100 + 26.765 t  4.905 t^2.
When t = 4.08, Y = 127 m
Your answer is incorrect.
Solve for t when Y = 0
Then multiply that time by 40 m/s*cos 42, the horizontal velocity component.
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