A-level Physics (Advancing Physics)/Stress, Strain & Young's Modulus/Worked Solutions

1. stress=force/cross-sectional area =100/(0.5x10^-6)m =2x10^8 Pa 2. cross-sectional area=force / stress =100N / 70MPa =1.428x10^-6 3. strain=extension/original length = 2/10 = 0.2 4. Decimal --> percentage = 0.2*100 = 20% 5. young modulus=stress/strain = (force/area)/(extension/length) = (force x length)/(area x extension) = (50 x 0.7)/(0.05 x (pi x 0.001^2) = 2.23x10^8 8. Tensile Strength = Force / Area = 0.95x10^6 = 25/A = 25 / 0.95x10^6 = A = A = 2.63x10^-5 9. force/area = (young modulus)(extension/length) = extension = ( length x force ) / ( area x young-modulus ) = ( length x force x 4 ) / ( pi x diameter^2 x modulus ) = ( 1E4 * 10 * 4) / ( 3.14159 x 4E-6 x 9E11 ) = 3.54E-2 meters = 3.54 cm 10. 10 Newton = mg = (kilograms)x(9.8 m/s/s) But you have to be careful here because although they say a kilogram "equals" about 2.2 pounds, the pound is a unit of force (not mass). Google replaces "equals" with "means", to obtain: kilograms = (10 / 9.8) = 1.020498 1 kg "means" 2.2046226218 Pounds (from Google) m "means" 1.020498 kg (2.2046226218 Pounds/kilogram) 10 Newtons "means" 2.25 pounds Or, just google how many pounds is 10 Newtons to get 2.248 Pounds. I don't know where I lost the .002 Pounds. I wouln't have written the question if I knew it was this hard!