Units and Conversions You may find the following units and conversions helpful. Metric system. Work is measured newton-metres (N - m) or joules (J). One joule is one newton-metre. Force, as well as weight, is measured in newtons (N). The weight of an object is the force acting on the object due to gravity, calculated by the formula weight = mass X g. The constant of acceleration due to gravity is g. Its unit is metres per second squared (m/sz). You may use the approximation g ~ 9.8 m/s?. Mass is measured in kilograms (kg). The density of water is 1 kg/L. Volume is measured in litres L. 1m?is 1000 L. Length is measured in metres (m). One centimetre is 0.01 metre. One millimetre is 0.001 metre. US Customary system. Work is measured in pound-foot (Ib-ft). Force, as well as weight, is measured in pounds (lb). Length is measured in feet (ft). A cable hangs off the roof of a 20-metre building. The cable weights 8 kilograms and is 5 metres long. You lift the cable by pulling from its top end. How much work does it take to lift the entire cable to the top of the building? Assume work is measured in newton-metres (N - m). Use a calculator to find a numerical approximation of your final answer to 2 decimal places. For example, if your final answer is 7, then you should enter 3.14 in the box below. In tests and the final exam, you will NOT need to approximate your final answer numerically