What is the equation for calculating a machine's efficiency?

I searched all over my textbook and couldn't find it, so I decided to post my question here.

Explain where in a spiral galaxy you would expect to find globular clusters, molecular clouds, and atomic hydrogen.

Cloudy nights can be warmer than clear nighys because clouds trap heat

What happens when you change the number of electrons in an atom

Where does the energy of an earthquake originate? A. Movement of tectonic plates B. the building of volcanoes C. Earth's magnetic field

Which of the following safety devices provides a weak link in a circuit that will melt if it received too much current, thus breaking the circuit and stopping the flow of electricity? a. circuit breaker b. fuse c. gfci d. insulation

the half-life of carbon - 14 is 5730 years. What fraction of carbon-14 would remain after 11,460 years?

An object with a mass of 10.9 kg experiences a force of 18.53 N. What is the acceleration of the object? A. 2.2 m/s2 B. 1.7 m/s2 C. 16.83 m/s2 D. 1.3 m/s2

A proton, starting from rest, accelerates through a potential difference of 1.0 kV and then moves into a magnetic field of 0.040 T at a right angle to the field. What is the radius of the proton's resulting orbit

Which of the following terms are needed to completely describe speed? Check all that apply. A. Units B. Direction C. Number D. Mass

Drivers are able to see objects ahead of them because light travels through windshields.