Question

If you were to drop a rock from a tall building, assuming that it had not yet hit the ground, and neglecting air resistance, after it has fallen 22 m:
How much time has passed (in s)?
what is the speed at this distance (in m/s)?

Answer 1

Since the object is dropped from some height so its initial speed must be zero

acceleration of the object is due to gravity

so we can use kinematics to find the time it will take to drop by x = 22 m

$\delta x = v_i * t + \frac{1}{2}at^2$

$22 = 0 + \frac{1}{2}*9.8*t^2$

$t = 2.12 s$

Now the speed after 2.12 s will be given as

$v_f = v_i + at$

$v_f = 0 + 9.8 * 2.12$

$v_f = 20.8 m/s$

so above is the speed and time