Which model would best demonstrate the role of gravity in the Solar System? O A. a large ball with 8 smaller balls arranged around it because gravity is between the sun and 8 planets O B. a magnet drawn close to another magnet because planets are dbvn towards the magnetism of the Sun O c. a football field with a pea at one end and a grain of sand at the other because the scale of gravity is large O D. a ball attached to a string moving in a circular motion because the string keeps the ball in place like gravity

The frequency of a tuning fork can be found by the method shown. a long tube open at both ends is submerged in a beaker of water, and the vibrating tuning fork is placed near the top of the tube. the length l of the air column is adjusted by moving the tube vertically. the sound waves generated by the fork are reinforced when the length of the air column corresponds to one of the resonant frequencies of the tube. the smallest value for l for which a peak occurs in sound intensity is 7 cm. l what is the frequency of the tuning fork? the speed of sound in air is 345 m/s. answer in units of hz