Answer:
1.55s
Step-by-step explanation:
The height equation of the projectile is given as;
h = -16t^2 + vt + s .......1
where;
t is the time in seconds,
v is the upward velocity at the start,
s is the starting height.
Given;
v = 70 ft/s
s = 5 ft
Substituting the values equation 1 becomes;
h = -16t^2 + 70t + 5
For the ball to reach 75 ft, h = 0
75 = -16t^2 + 70t + 5
-16t^2 + 70t + 5 - 75 = 0
-16t^2 + 70t - 70 = 0
solving the quadratic equation;
Time t = 2.83 s and t = 1.55s
Therefore, the ball will first reach 75 ft after 1.55 seconds.
