A closed system consists of a pendulum that is swinging back and forth. If the pendulum's kinetic energy decreases, what else must happen to the
energy of the system?
A. Its gravitational potential energy must decrease.
B. Its total mechanical energy must increase.
C. Its total mechanical energy must decrease.
D. Its gravitational potential energy must increase.

You are traveling in a car going at a constant speed of 100km/h down a long, straight highway. you pass another car going in the same direction which is traveling at a constant speed of 80km/h. as measured from your car's reference frame this other car is traveling at −20km/h. what is the acceleration of your car as measured from the other car's reference frame? what is the acceleration of the other car as measured from your car's reference frame?

Air is contained in a variable-load piston-cylinder device equipped with a paddle wheel. initially, air is at 400 kpa and 17°c. the paddle wheel is now turned by an external electric motor until 75 kj/kg of work has been transferred to air. during this process, heat is transferred to maintain a constant air temperature while allowing the gas volume to triple. calculate the required amount of heat transfer in kj/kg.

This is one type of line graph in which the independent variable is time plotted on the x axis and the dependent variable, also numerical, is plotted on the y axis.