What branch of physics is it related to? The Gravity Light

Which of the following is an example of units for speed

The experiment done in lab is repeated, using a ball that has unknown mass m. you plot your data in the form of f 2 versus m/l, with f in rev/s, m in kg, and l in m. your data falls close to a straight line that has slope 3.19 m/(kg · s2). use g = 9.80 m/s2 and calculate the mass m of the ball.

An element becomes a positively charged ion when itloses protons.loses electrons.gains electrons.gains neutrons.