The useful power out of an electric motor is 20w and the total power into the motor is 80w calculate the percentage efficiency of the motor

Select the word from the list that best fits the definition classification of most stars on the h-r diagram

Asystem containing an ideal gas at a constant pressure of 1.22×10^5 pa gains 2140 j of heat. during the process, the internal energy of the system increases by 2320 j. what is the change in volume of the gas?

When you push downward on a book at rest on a table, you feel an upward force. does this force depend on friction? defend your answer.