Question #a91b2

1 Answer
Oct 17, 2016

A ball is thrown upward in the air, and its height above the ground after t seconds is H(t)=83⋅t-16t^2H(t)=83t16t2 feet.

Differentiating w.r.to t we get the upward velocity v(t)uparrowv(t) after t sec.

So

v(t)uparrow=(dH(t))/(dt)=d/(dt)(83t-16t^2)v(t)⏐ ⏐=dH(t)dt=ddt(83t16t2)

=>v(t)uparrow=83-32t......(1)

when the ball will be traveling downward at 41.5 feet per second,then
v(t)uparrow=-41.5" ft/s"

Inserting this value in (1) we get

v(t)uparrow=83-32t

=>-41.5=83-32t

=>t=124.5/32=3.89s

So the ball will be traveling downward at 41.5 feet per second after 3.89s of its projection upward from the ground.