F varies directly with m and inversely with the square of d

F varies directly with m and inversely with the square of d. If F=60 when m = 180 and d = 3, find F when m = 1250 and d = 5

Solution

F is directly proportional to m and inversely proportional to square of d;
So let\'s say that F is proportional to m/d^2;
F= K* M / D^2 (where K is the constant of propotionately)
When F= 60; m = 180 and d=3;
substituting these values in the above equation we get
60= k* 180/ 3*3; Thus 60= K*20; K= 60/20=3

Thus K = 3 (we now have the value of the constant of proportionately)

Now substitute this is the equation
F= 3*1250/(5*5)= 3* 50= 150;

Thus when m=1250 and d=5 we get F=150;