Question

Irene hits a golf ball off the ground with an initial upward velocity of 45 m/s. which equation can be used to find the amount of time, t, it will take to hit the ground?

A. -16t^2+45=0
B.-16t^2+45t=0
C.-4.9t^2+45=0
D.-4.9t^2+45t=0

Answer 1

The acceleration due to Earth's gravity is customarily considered to be -9.8 m/s² for algebra problems, so the value in equations C and D is appropriate to the problem dimensions (m/s). (The equation for ballistic motion uses (1/2)*g = -4.9 m/s².)

Equation C has the initial height of the ball as 45 m, with no vertical velocity. Equation D has the vertical velocity as 45 m/s.

The appropriate choice is ...
D. -4.9t^2+45t = 0