Engineers who design battery-operated devices such as cell phones and mp3 players try to make them as efficient as possible. an engineer tests a cell phone and finds that the batteries supply 10,000 j of energy to make 5500 j of output energy in the form of sound and light for the screen. how efficient is the phone?

According to newton's second law, when the same force is applied to two objects of different masses, a the object with greater mass will experience a great acceleration, and the object with less mass will experience an even greater acceleration, b. the object with greater mass will experience a smaller acceleration, and the object with less mass will experience a greater acceleration, c. the object with greater mass will experience a greater acceleration, and the object with less mass will experience a smaller acceleration, d. the object with greater mass will experience a small acceleration, and the object with less mass will experience an even smaller acceleration.

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.

Positrons are spontaneously emitted from the nuclei of