Question

A brick is thrown from a wall that is 19.2 m above the ground and hits the ground 5.00 s later. What was the initial velocity of the brick?

A) -8.80 m/s
B) 1.00 m/s
C) -28.4 m/s
D) 20.6 m/s"

Answer 1

The initial velocity of the brick can be found by using the kinematic equations for uniformly accelerated motion, specifically factoring in the distance fallen, time taken, and the acceleration due to gravity.

Step-by-step explanation:

To determine the initial velocity of the brick thrown from the wall, we can use the kinematic equation for uniformly accelerated motion, which in this case is due to gravity. The equation that relates displacement (Δy), initial velocity (v_i), time (t), and acceleration (a) is:

Δy = v_i × t + ½ × a × t^2

We know that the brick hits the ground after 5 seconds (Δy = -19.2 m, considering downward direction as negative), the acceleration due to gravity (a = -9.8 m/s², the negative sign indicates that acceleration is downward), and the time it takes to hit the ground (t = 5.00 s). Plugging these values into the equation, we can solve for the initial velocity (v_i)

Using the following: Δy = -19.2 m, t = 5.00 s, and a = -9.8 m/s²:

-19.2 m = v_i × 5.00 s + (½ × -9.8 m/s² × (5.00 s)^2)

By solving for v_i, we find the initial velocity of the brick.