Final answer:
The iPhone's speed after 3 seconds is 29.4 m/s.
Step-by-step explanation:
The iPhone's speed after 3 seconds can be determined using the equations of motion. Assuming the initial velocity is 0 m/s and the acceleration due to gravity is 9.8 m/s²:
Using the formula v = u + at, where v is the final velocity, u is the initial velocity, a is the acceleration, and t is the time:
v = 0 + (9.8)(3) = 29.4 m/s