A machine has an efficiency of 15% . If the energy inputs is 300 joules, how much useful energy is generated

Which statement is true? a. kepler's laws apply only to the motion of earth. b. kepler's laws can be used to predict eclipses. c. kepler's laws are true for a central force that is directly proportional to distance. d. kepler's laws can be deduced from newton's laws of motion and gravity.

What are the north and south poles of a solenoid change with?

The ph is the a.independent variable b.the dependent variable c.control group