The normal force (FN) refers to is?

If the chemical properties of a substance remain unchanged and appearance or shape of a substance changes it is called a ?

6–43 a food department is kept at 2128c by a refrigerator in an environment at 308c. the total heat gain to the food department is estimated to be 3300 kj/h and the heat rejection in the condenser is 4800 kj/h. determine the power input to the compressor, in kw and the cop of the refrigerator.

What is friction? how does it affect the motion of an object?