Which statement about the acceleration of an object is correct? a. The acceleration of an object is directly proportional to the net external force acting on the object and inversely proportional to the mass of the object.

b. The acceleration of an object is directly proportional to the net external force acting on the object and directly proportional to the mass of the object.

c. The acceleration of an object is inversely proportional to the net external force acting on the object and inversely proportional to the mass of the object.

d. The acceleration of an object is inversely proportional to the net external force acting on the object and directly proportional to the mass of the object.

The law of conservation of energy states that energy cannot be created or , energy can be from one substance to another. the first blank is ' destroyed ' and for the second blank is ' transferred '

Under conditions for which the same room temperature is maintained by a heating or cooling system, it is not uncommon for a person to feel chilled in the winter but comfortable in the summer. provide a plausible explanation for this situation (with supporting calculations) by considering a room whose air temperature is maintained at 20â°c throughout the year, while the walls of the room are nominally at 27â°c and 14â°c in the summer and winter, respectively. the exposed surface of a person in the room may be assumed to be at a temperature of 32â°c throughout the year and to have an emissivity of 0.90. the coefficient associated with heat transfer by natural convection between the person and the room air is approximately 2 w/m2 â‹…â‹… k. what is the ratio of the thermal resistance due to convection to the thermal resistance due to radiation in the summer? what is the ratio of thermal resistances in the winter

At very high pressures, gases become and will eventually a) more dense; become hotter b) more dense; change to a liquid or solid c) less dense; combust d) less dense; turn into a liquid