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The equation y = -6t^2 + 51t describes the height (in feet) of a projectile launched from the surface of Mars at 51 feet per second. In how many seconds will the projectile first reach 108 feet in height?

 Nov 25, 2019
 #1
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2 second= 51+51=102 feets 

in 1/100 second, 0.51 feet is climbed 

well 108-102 feets = 6 feets

We know that 1/100 second = 0.51 feet 

so in order to find these 6 feets

0.51 *x= 6 

Specific number of seconds is multiplied to find the feets 

x=6/0.51=11.764 approx.=11.8 

 

2:11.8 (Second, second/100) 

approx

2 seconds and 11.8 sec/100

2.12 seconds!  

 Nov 25, 2019
 #2
avatar+105476 
+1

We need to solve this

 

108 = -6t^2 + 51t       rearrange as

 

6t^2 - 51t + 108  = 0        divide through by 3

 

2t^2 - 17t  +  36   = 0       factor

 

(2t - 9) (t  - 4)    = 0

 

Set both factors to 0  and solve for t

 

2t  - 9    = 0                         t  - 4   = 0         

2t   = 9                                t  = 4 sec

t  =9/2  = 4.5 sec

 

It first reaches 108 ft  at  4 sec

 

 

cool cool cool

 Nov 25, 2019
 #3
avatar+10810 
+2

The equation y = -6t^2 + 51t describes the height (in feet) of a projectile launched from the surface of Mars at 51 feet per second. In how many seconds will the projectile first reach 108 feet in height?

laugh

 Nov 25, 2019

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