Many sources of energy such as nuclear, coal, and oil use a fuel source to turn water into steam. The steam is then used to turn a turbine and generate electricity. Why are these sources not very efficient?

An airplane flies eastward and always accelerates at a constant rate. at one position along its path it has a velocity of 34.3 m/s, it then flies a further distance of 40100 m and afterwards its velocity is 47.5 m/s. find the airplane\'s acceleration and calculate how much time elapses while the airplane covers those 40100 m.