Solve a given formula

[justan4cat]

I got most of this one, I think but I get stuck at the radical. I'm not sure what I'm doing to it is right. Directions say to use s=16t^2 to solve the problem.

s=distance in ft. that an object falls freely from rest; t=seconds

How long would it take an object to fall freely from a bridge 725 feet above the water?

s=725 ft. t is unknown

725=16t^2 divide both sides by 16
725/16=t^2
t=+/- sqrt 725/16
t=+/- sqrt 256/16+469/16
t=4 +/- sqrt 469/16
ok... now what do I do with the sqrt of 469/16? Calculate it to the nearest 10th?

 

[BigGlenntheHeavy]

\(\displaystyle Distance \ formula: \ S(t) \ = \ -16t^2+V_o(t)+S_o\)

\(\displaystyle Hence, \ 0 \ = \ -16t^2+725, \ V_o \ = \ 0\)

\(\displaystyle 16t^2 \ = \ 725, \ t^2 \ = \ \frac{725}{16}, \ t \ = \ \sqrt\frac{725}{16} \ \dot= \ 6.73 \ sec.\)

 

[Deleted member 4993]

I got most of this one, I think but I get stuck at the radical. I'm not sure what I'm doing to it is right. Directions say to use s=16t^2 to solve the problem.

s=distance in ft. that an object falls freely from rest; t=seconds

How long would it take an object to fall freely from a bridge 725 feet above the water?

s=725 ft. t is unknown

725=16t^2 divide both sides by 16
725/16=t^2
t=+/- sqrt 725/16
t=+/- sqrt (256/16+469/16)

t=4 +/- sqrt 469/16 <<< This step is incorrect
ok... now what do I do with the sqrt of 469/16? Calculate it to the nearest 10th?

Since the data given to you (s = 725) has 3-significant digits - that is how far you should go.

t = sqrt (725/16) = 6.731456009 = 6.73 seconds