+0  
 
0
243
1
avatar+946 

A model rocket is launched off the top of a platform. The height of the rocket is given by the function h(t) = -4.9t2 + 86t + 2.1, where h(t) is the height in metres and t is the time in seconds. 
a) When will the rocket’s height be 200 m?
b) How long will it take for the rocket to reach the ground?

Julius  Apr 4, 2017
 #1
avatar+87333 
+2

a)   200 =  -4.9t^2 + 86t + 2.1     subtract 200 from both sides

 

0  =  -4.9t^2 + 86t - 197.9    using the quadratic formula.....we have

 

t  =    [ -86 ± √ [ (86)^2  - 4 ( -4.9) (-197.9) ] ]  /  (2 * - 4.9)

 

Evaluating this.....we have that ....   t  ≈ 2.7 seconds  and t ≈ 14.8 seconds

 

 

b)  0  = -4.9t^2 + 86t + 2.1  

 

Again, using the quadratic formula we have  ≈    17.575 seconds

 

 

 

cool cool cool

CPhill  Apr 4, 2017

9 Online Users

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.