Word Problem re:distance object thrown

[Becky4paws]

Word problems have always scared me.

If an object is thrown vertically upward fromthe ground with an initial speed of 160 feet per second, its height (in ft.) t seconds later is given by the function H(t) = -16t^2 + 160t.

a. Graph the function H(t).
b. Use the graph in part (a) to determine when the object will hit the ground.
c. Use the graph in part (a) t estimate howhigh the object wil rise.

I first would solve for H(t):
H(t)=-16t^2+160t

Factoring out the 16t gives H(t)=16t(t+10)
H(t) = t=-10.

That itself doesn't seem right to me. Can you nudge me in the right direction?

 

[skeeter]

h(t) = -16t^2 + 160t
h(t) = -16t(t - 10)

 

[Becky4paws]

Now how do I tell from the graph
b. when the object will hit the ground
c. how high the object will rise

On part b, I assume that I solve H(10) = -16(10)^2+160(10)
Giving me H(10)=-16(10)^2+160(10)
H(10)=-16(100)+1600
H(10)=-1600+1600
H(10)=0
So the object will hit the ground at (10,0) on a graph

For the next part on how high the object will go, do I just find solutions for H(t) when t>10?

 

[skeeter]

the graph of h(t) is an inverted parabola ... find its vertex to get the max height.