# Need help with motion of particle question (1 Viewer)

#### kevinsta

##### Member
A projectile is fired into the air
and its height in metres is given
by h = 40t − 5t^2 + 4, where t is in
seconds.

(d) What is the maximum height

#### photastic

##### Well-Known Member
Max height when dh/dt = 0. This is why at the highest point the path looks like the vertex of a parabola.
So make dh/dt = 0 and find the time it takes to reach the highest point, then subbing it back into h.

Last edited:

#### randomly_generated

##### Member
Max height when dh/dt = 0. This is why at the highest point looks the path like the vertex of a parabola.
So make dh/dt = 0 and find the time it takes to reach the highest point, then subbing it back into h.
This. AND make sure you test if it is a maximum, remember a parabola could have a max or min

#### faisalabdul16

##### Wot
Max height when dh/dt = 0. This is why at the highest point the path looks like the vertex of a parabola.
So make dh/dt = 0 and find the time it takes to reach the highest point, then subbing it back into h.
Yeap!

you should get 84

#### kevinsta

##### Member
Max height when dh/dt = 0. This is why at the highest point the path looks like the vertex of a parabola.
So make dh/dt = 0 and find the time it takes to reach the highest point, then subbing it back into h.
I thought when you make the velocity = 0 thats when it rests.

#### photastic

##### Well-Known Member
I thought when you make the velocity = 0 thats when it rests.
It also means max distance, same with max velocity when a=0

#### braintic

##### Well-Known Member
It also means max distance, same with max velocity when a=0
In both cases, there should be a 'possible' in there.

#### kevinsta

##### Member
It also means max distance, same with max velocity when a=0
do you know how i can find how far the projectile will travel in the first 4 seconds?