When t is 0,H = -16t² + h = -16*0² + 30 = 30 ft (30 feet higher than the ending point,the lower cliff)
When the vehicle reaches the lower cliff,H = -16t² + 30 = 0
t = √30/4
During this period (√30/4 seconds),the vehicle must travel at least 100 feet horizontally.The speed is 60 miles/hour,which is 60*5280 ft/3600 second
In √30/4 second,the vehicle travels (√30/4)(60*5280/3600) = 120 ft
Which is more than the 100 feet gap,so the batman can reach the lower cliff.
再问： wow holy! did you finish this Q by yourself?!
再答： yes. It's really simple.
