Solve this physics problem

Question

You work at a garden store for the summer. You lift a bag of fertilizer with a force of 130 N, and it moves upward with an acceleration of 0.763 m/s².(a) What is the mass of the fertilizer bag? (b) How much does the fertilizer bag weigh?

Answer 1

Hi Elle,

A part of the upward vertical force F=130N is to compensate the weight of the bag at rest W₀=mg=9.81m N, and the balance (F-W₀) would give the body the upward acceleration a=0.763m/s²

So, the mass of the bag s found from 2nd Newtonian Law

F-mg=ma => m(a+g)=F => m=F/(a+g)=130N/(0.763+9.81)m/s²=0.168kg

The (apparent) weight W_a is the force with which the bag is pulling down on you as you are lifting it. That force, by the 3rd Newtonian Law,

must be equal in size but directed opposite to the force F=130N you are pushing the bag up.

Best,

Dr.Ariel B.