They both flow in currents. Water has a pump that works like a battery and pipes that work like a circuit.
Locke said that under natural law, all people have the right to life, liberty, and private property; under the social contract, the people could instigate a revolution against the government when it acted against the interests of citizens, to replace the government with one that served the interests of citizens.
That is because there are other forces like the friction forces that apply differently on both of them. The frictional forces applied to the sled are smaller than they are on the father, for example, so it's possible for him to pull it.