Gravity increased the downward speed (or decreases the upward speed) by 9.8 m/s every second.
21.2/9.8 = 2.2 seconds
Answer:

Explanation:
It is given that,
Angular speed of the football spiral, 
Radius of a pro football, r = 8.5 cm = 0.085 m
The velocity is given by :


v = 3.68 m/s
The centripetal acceleration is given by :



So, the centripetal acceleration of the laces on the football is
. Hence, this is the required solution.
Answer:
5.057 m/s^2
Explanation:
Force of kinetic friction = .3 = F /normal force
.3 = F /(50* 9.81) F of friction = 147.15
Net force = 400 - 147.5 = 252.85 N
F = m * a
252.85 = 50 * a a = 5.057 m/s^2