Suppose the wavelength of the light is 450 nm . how much farther is it from the dot on the screen in the center of fringe e to the left slit than it is from the dot to the right slit?

Since you are looking at a right fringe, the answer is all the time a multiple of the wavelength for the reason that the light makes constructive intrusion. If you are looking at the center (zeroth) fringe, the difference is (450)(0) = 0. For the first maximum, the difference is 450 nm. For the second, it is 450 x 2 = 900 nm. Basically, for the nth maxima, the difference is 450n. 

a charge 3q is at the origin, and a charge −2q is on the positive x axis at x=a. part a where on the x-axis would you place a third charge so it would experience no net electric force? enter an expression for the exact answer, which will involve a square-root sign. (do not enter an approximate decimal answer.)

initial speed when it is dropped is 150 ft/s

now at the same moment the acceleration due to gravity is perpendicular to its velocity

so as we know that

now we have centripetal acceleration a = 32 ft/s^2 as its perpendicular to velocity

while tangential acceleration at the same moment will be zero

so

now radius of curvature is given as

so the radius of curvature just after it is dropped is 703.125 ft