Question

a key is dropped from a height of 30 m , If its distance from the ground at t seconds after the release is given by the position function d (t) = 30-5t², find
a.its height velocity and acceleration after 1 second.
b. the time it reached the ground.
c. its position after 1 second

Answer 1

If d(t) = 30 - 5t^2 m, then the velocity is
v(t) = -10t m/sec , and the acceleration is
a(t) = -10 m/sec^2

(each is the derivative of the previous function)

a) when t = 1
distance = 30 - 5(1^2) = 25 m
velocity = -10(1) = -10 m/s
acceleration = -10 m/s^2

b) when it reaches the ground, d(t) = 0, so
0 = 30 - 5t^2
t^2 = 6
t = √6 or appr. 2.4 seconds

c) 25 m above the ground , already answered in a)