# calculus HELP!

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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 HELP! -

Calculus? Hardly.

vf=vi+gt for the firstquestion

second question: h=vi*t-4.9t^2 Vi=0, solve for t

third question
hf=hi+vi*t-4.9t^2
0=100+8t-4.9t^2
solve for time t, then vf=vi-9.8t

but there is an easier method for the last:

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