A-level 物理（高级物理）/应力、应变和杨氏模量/解答

1. 应力 = 力 / 横截面积

    =100/(0.5x10^-6)m
    =2x10^8 Pa

2. 横截面积 = 力 / 应力

     =100N / 70MPa
     =1.428x10^-6

3. 应变 = 伸长量 / 原长

     = 2/10
     = 0.2

4. 小数 --> 百分比

     = 0.2*100 
     = 20%

5. 杨氏模量 = 应力 / 应变

     = (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. 抗拉强度 = 力 / 面积

     = 0.95x10^6 = 25/A
     = 25 / 0.95x10^6 = A
     = A = 2.63x10^-5

9. 力 / 面积 = (杨氏模量)(伸长量 / 长度)

     = 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 牛顿 = mg = (千克)x(9.8 米/秒/秒)

但你必须小心，因为尽管他们说一公斤“等于”大约 2.2 磅，但磅是力的单位（而不是质量）。谷歌将“等于”替换为“表示”，以获得

    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!