+0  
 
0
234
2
avatar

I got this problem I can't wrap my head around. help?

 

H(T) =-4.9t^t + 40t

 

when hight (H) is 75, what is seconds (T)

Guest May 8, 2017
 #1
avatar+7324 
+4

I think this is what the equation is:

H(t) = -4.9t^2 + 40t

 

We want to know what t is when h(t) = 75

So plug in 75 for h(t) and solve for t.

75 = -4.9t^2 + 40t

 

Subtract 75 from both sides.

0 = -4.9t2 + 40t - 75

 

Now we can use the quadratic formula to solve for t.

\(t = {-40 \pm \sqrt{40^2-4(-4.9)(-75)} \over 2(-4.9)}\\~\\t={-40 \pm \sqrt{130} \over -9.8}\\~\\ t=\frac{-40+\sqrt{130}}{-9.8}\qquad\text{or}\qquad t=\frac{-40-\sqrt{130}}{-9.8}\)

 

t ≈ 5.245 seconds      or      t ≈ 2.918 seconds

hectictar  May 9, 2017
 #2
avatar+7324 
+4

Maybe this graph can help you wrap your head around it smiley

 

Imagine you threw a baIl up in the air and every second you wrote this information down: (what second it was, the height of the ball at that second). For example....at second 1, the height was 35.1 units...and you would write down: (1, 35.1).

 

Then you plotted all these points on a graph and drew a red line connecting the points. This is what your line would look like:

 

 

And the question is, " After how many seconds was the ball was 75 units up in the air? "

hectictar  May 9, 2017

42 Online Users

avatar

New Privacy Policy

We use cookies to personalise content and advertisements and to analyse access to our website. Furthermore, our partners for online advertising receive information about your use of our website.
For more information: our cookie policy and privacy policy.