calculus HELP!
posted by Danielle on .
A person stands on a bridge that is 100 feet above a river.
If she drops a pebble how fast is it moving after 2 seconds?
How long does it take the pebble to reach the river below?
She has another pebble that she tosses up with initial speed of 8 feet per second. It goes up, then starts falling down to the river below. By the time it reaches the river what is its speed?

Calculus? Hardly.
vf=vi+gt for the firstquestion
second question: h=vi*t4.9t^2 Vi=0, solve for t
third question
hf=hi+vi*t4.9t^2
0=100+8t4.9t^2
solve for time t, then vf=vi9.8t
but there is an easier method for the last:
vf^2=vi^2+2ad where a=9.8, d=100