Answer:
At the maximum height the ball will have an instantaneous velocity of zero. The formula for instantaneous velocity is
v = v₀ + at
Where v is the instantaneous velocity, v₀ is the initial velocity, a is the acceleration due to gravity, -9.8 m/sec², and t is the time.
We need instantaneous velocity to = 0.
0 = 20 - 9.8t : Isolate t => 1st step: Add 9.8t to both sides
9.8t = 20 : Isolate t => 2nd step: Divide both sides by 9.8
t = 2.04 seconds (approximately)
Step-by-step explanation: