An object is thrown straight down with an initial speed of 4 m/s from a window which is 8 m above the ground.The time it takes the object to reach the ground is:
A)0.80 s
B)0.93 s
C)1.3 s
D)1.7 s
E)2.0 s

Question

Quizplus · Accepted Answer

We can use the kinematic equation:
d = vi*t + (1/2)*a*t^2

where
d = distance traveled (8 m)
vi = initial velocity (4 m/s)
a = acceleration due to gravity (-9.8 m/s^2)
t = time taken to reach ground (unknown)

Plugging in the values, we get:
8 = 4t + (1/2)*(-9.8)*t^2
0 = 4t - 4.9t^2
0 = t(4 - 4.9t)

Solving for t, we get t = 0.93 s (rounded to two decimal places). Therefore, the best choice is B.

An Object Is Thrown Straight Down with an Initial Speed