Coins were developed as a medium of exchange because other items like cows, grain, and land were more difficult to move from place to place. true or false?

Imagine that someone pushes one marble toward a motionless marble. would there still be action-reaction forces involved in the collision? how might the marbles’ motions be changed? ?

In a good thermo flask the main cause of heat loss is

Which is a substance that can be separated by physical means and is not the same throughout