Question

1.
A rock is thrown upward with a velocity of 12 meters per second from the top of a 28
meter high cliff, and it misses the cliff on the way back down. When will the rock be 5
meters from ground level? Round your answer to two decimal places.
Gravity Formula


PLS HELP

Answer 1

Answer:

The rock will be be 5  meters from ground level at time = 3.713 seconds

Step-by-step explanation:

As we know-

$s(t) = -4.9 * t^2 + v_0t + s_0$

V0 = velocity

S0 = height above ground when thrown

Substituting the given values, we get -  

$9 = -4.9* t^2 + 12 * t +32\\-4.9*t^2 +12*t + 23 = 0$

As per the formula

$t = \frac{-12+ \sqrt{12^2 -4*(-4.9)*23} }{(2*(-4.9)} \\t = 3.713$

The rock will be be 5  meters from ground level at time = 3.713 seconds