An object is thrown upwards with a speed of 13 m/s. How long does it take to reach a height of 4.0 m above the projection point while descending?
A) 0.42 s
B) 1.2 s
C) 2.3 s
D) 3.1 s
E) 4.2 s

Question

Quizplus · Accepted Answer

We can use the kinematic equation:

h = vi*t - 0.5*g*t^2

where h is the height, vi is the initial velocity, g is the acceleration due to gravity (-9.8 m/s^2), and t is time.

Since the object is descending, its initial velocity is negative (-13 m/s). Plugging in the given values and solving for t:

4.0 m = -13 m/s * t - 0.5 * (-9.8 m/s^2) * t^2

t^2 + (13/9.8) * t - 0.816 = 0

Using the quadratic formula (or factoring), we get:

t = 2.3 s (rounding to one decimal place)

Therefore, the object takes 2.3 s to reach a height of 4.0 m above the projection point while descending.

An Object Is Thrown Upwards with a Speed of 13