Factoring - Word Problem

Question

Investigators at a traffic accident use the equation: D=0.04v^2 + 0.8v where v is teh velocity (speed in mph) of the car before starting to stop and D is the stopping distance (length of the skid marks). If the skid marks are 192 feet long, how fast was the car traveling prior to the accident? Please show all steps.

Answer 1

Hi,

 

0.04v^2+0.8v-192 = 0

 

Dividing all terms by 0.04

 

v^2 +20v - 4800 = 0

 

(v-60)(v+80) = 0

 

v = 60 or -80

 

Since, velocity cannot be negative, we will drop -80 mph and keep 60 mph as our final answer.

 

Gaurav