Question

a projectiles height, in feet, t seconds after launch is given by the function h(t)=-10t^2+100t
A) find the time t when the projectile reaches its maximum height

Answer 1

The projectile reaches its maximum height when the velocity changes it's direction, this is, when velociti is 0.
Now the velocity is given by the first derivative (Of couse this also can be done without using derivatives. ) of the ecuation that describes movement, so at t second, the velocity is:
v(t)=h'(t)=-10t+100

So we have that at the maximum height

-10t+100=0
Now just solve for t.

Answer 2

* -20t+100=0

Answer 3

5 thank you

Answer 4

Welcome