A stainless-steel orthodontic wire is applied to a tooth. The wire has an unstretched length of 3.1 cm and a diameter of 0.22 mm. If the wire is stretched 0.10 mm, find the magnitude and direction of the force on the tooth. Disregard the width of the tooth, and assume that Young's modulus for stainless steel is 18 x 10^10 Pa. With the question there is a picture of a bent wire with a tooth sitting the the middle and two 30 degree angles on either side. I guess I don't understand this stuff as much as I thought I did because I cannot come up with the correct answer. Here is what I did: 1. I converted everything to meters 2. I found delta L by taking .031 m -.00010 m = 3.09 x 10 -2 m 3. I found the A of the wire with 2(pie)r^2 + 2(pie)rh = 2(pie)(1.1 x 10 ^-4)^2 + 2(pie)(1.1 x 10 ^-4)(.031 m) = 2.15 x 10 ^-5 m^2 4. Then I plugged all my info into this equation: F = yA/Lo * delta L and I can't come up with the right answer. I keep getting 3.86 x 10 ^-2 but I am supposed to get 22N. I am way off! Can somebody please help get me back on the right track!?