So that we do not contaminate it with microorganisms or garbage or other human stuff.
Maybe the picture helps. The blue block represents the cart with a mass of 3 kg. The person(black block) is pulling the cart to the right with a force F so that the acceleration a is 2 m/s². According to Newton's 2nd law: F = m*a.
Answer:B
Explanation:sorry they removed my answer for some reason.
Gravity as all bodies whether large or small have mass.