A ball is thrown straight upward from ground level with a speed of 18 m/s. How much time passes before the ball strikes the ground if we disregard air resistance?
A)3.7 s
B)1.8 s
C)1.1 s
D)0.6 s

Question

Quizplus · Accepted Answer

We can use the equation:

h = ut + (1/2)at^2

Where,
h = final height (which is 0 in this case)
u = initial velocity = 18 m/s
a = acceleration due to gravity = -9.8 m/s^2 (negative because it is acting in the opposite direction to the initial velocity)
t = time

Substituting the values, we get:

0 = 18t - (1/2)×9.8×t^2

Simplifying, we get:

4.9t^2 - 18t = 0

Factorizing, we get:

t(4.9t - 18) = 0

Therefore, t = 0 or t = 18/4.9

Since we are looking for the time before it strikes the ground, we can ignore the t = 0 solution.

Therefore, t = 18/4.9 = 3.7 seconds (approx).

A Ball Is Thrown Straight Upward from Ground Level with a Speed