Imagine you fill an insulated cup almost full with chopped or crushed ice, and measure the temperature after a minute or two, once it’s all come to thermal equilibrium. Since this ice is frozen water, the temperature should be at 0°C or not more than a couple of degrees below. Then, imagine you add a bunch of salt and stir it around.

What do you think the lowest temperature you can attain will be? Why? What happens to the amount of liquid present if you keep stirring and adding salt? How can we understand this phenomenon in terms of thermal and bond energy systems?

Develop an explanation for the changes you would observe in this physical system (decrease in temperature and change of phase) in terms of the Energy-Interaction Model. Preview the document

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.

the moving of the box is a result of centripetal force. think of that  as a car or a truck in this case creates a turn, the force of friction performing upon the turned wheels of the car runs centripetal force obligatory for circular motion for the things inside it.