Question

The power P (in watts) generated by a windmill that has efficiency E is given by the formula P = 0.31ED^2V^3, where D is the diameter (in feet) of the windmill blades and V is the wind velocity (in ft/sec). Approximate the wind velocity necessary to generate 30,000 watts if E = 41% and D = 17

Answer 1

You can try to solve by plugging in the values that they gave you

P = 30,000
E = 41% but change it to a decimal and it becomes .41
D = 17
V = ? the value you are trying to find

so......

using the formula: P = 0.31ED^2V^3

30,000 = (0.31)(0.41)(17^2)(V^3)
30,000 = (36.7319)(V^3)
30,000/36.7319 = V^3
816.7287834 = V^3
 you have to get the cubic root
∛816.7287834
your answer should be higher than 9 but lower than 10
 with whatever number you get plug it into the formula again and then check to see if your answer comes out to 30,000

hope this helps :)