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The formula d=16t squared represents the approximant distance d in feet a skydiver falls in t seconds before opening the parachute. The formula assumes that the

The formula d=16t squared represents the approximant distance d in feet a skydiver falls in t seconds before opening the parachute. The formula assumes that there is no air resistance. How long does it take a skydiver take to fall 816 feet before opening the parachute?
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1 Answer

First - you should learn   the formula  d = (1/2)gt2 = (1/2)(32ft/s2)(t2)
Using the formula  d=16t  hides the physics of what is really happening.
The 32 (or 32.2) feet per seconds squared is the acceleration caused by gravity near the earths surface.
The formula you gave does not work everywhere in the universe - d = (1/2)gt2 works everywhere in the universe.
 
SO to your problem...
You need to solve the formula for the unknown T.
 
d = (1/2)gt2   multiply both sides by 2
 
2d = gt2     divide both sides by g
 
2d/g = t2   take the square root of both sides
 
√(2d/g) = t   switch it awound to get the unknown on the left
 
t = √(2d/g)   now just plug in the numbers and calculate
 
t = √ [ 2(816 ft)/32 ft/s2 ] =

Comments

It is always better to do the algebra and solve for the unknown FIRST.
Before you plug in any numbers.
That way:
1) You can check the units to see if they are right before you calculate.
     No sense in calculating if you have things wrong.
2) Sometimes doing the algebra will show things that cancel out.
     The the calculation gets easier.
3) If you put the numbers in first, and then try to punch them into the calculator;
     You will be trying to do algebra in your head.
     And you WILL make mistakes sometimes.
     You are just learning algebra - Don't try to do it in your head.