Johnny is pulling a 15 kg box on carpet to the right. If the coefficient of friction of the carpet is m=0.3. What is the frictional force exerted on the box by the carpet?
a
45 N
b
-4.5 N
С
-45 N
d
4.5 N

A500g object falls off a cliff and losers 100 j from its gravitational potential energy store. if the gravitational field strength g=9.8n/kg, how high is the cliff?

How is sound energy produced a. vibrating objects b. objects being heated c. temperature differences d. stationary objects

Air enters a gas turbine with two stages of compression and two stages of expansion at 100 kpa and 17°c. this system uses a regenerator as well as reheating and intercooling – the intercooler returns the air to the inlet temperature. the pressure ratio across each compressor is 4 ; 300 kj/kg of heat are added to the air in each combustion chamber; and the regenerator operates perfectly while increasing the temperature of the cold air by 20°c. determine the system’s thermal efficiency. assume isentropic operations for all compressor and the turbine stages and use constant specific heats at room temperature. (0.378)