In at least 150 words, justify the need for a control in an experiment. use complete sentences.
btw this is physical science

What is the force that opposes motion and works against the downward pull? a) friction b) gravity c) weight d) acceleration

Which compound is held together by the electrostatic force between two ions? a. co2 b. cci4 c. h2s d. mgf2

At 20∘c, the hole in an aluminum ring is 2.800 cm in diameter. you need to slip this ring over a steel shaft that has a room-temperature diameter of 2.804 cm . 1. to what common temperature should the ring and the shaft be heated so that the ring will just fit onto the shaft? coefficients of linear thermal expansion of steel and aluminum are 12×10−6 k−1 and23×10−6 k−1 respectively.