Question

Emma hits a golf ball from the ground with an initial vertical velocity of 40 m/s. Which equation can be used to find the time, t, it takes for the ball to reach the ball to reach the ground?

a. –16t2 + 40t = 0.
b. –16t2 + 40 = 0.
c. –4.9t2 + 40 = 0.
d. –4.9t2 + 40t = 0.

Answer 1

option d: - 4.9t2 + 40t = 0

Explanation:

This is a vertical movement with constant acceleration (which is the acceleratin of gravity: -9.8 m/s2)

The vertical position of the golf ball can be calculated with the equation:

S = So + Vo*t + a*(t^2)/2

Where S is the final position, So is the inicial position, Vo is the inicial speed, a is the acceleration and t is the time.

So, using So = 0, Vo = 40 and a = -9.8, we have:

S = 0 + 40t - 4.9t^2

To find the time when the ball reaches the ground, we just need to make S = 0, so:

- 4.9t^2 + 40t = 0

The correct option is (d)