If a 28-N force causes a rock to accelerate at 4 m/s/s, what is the mass of the rock?

7kg

Explanation:

Given parameters:

Force on the rock  = 28N

Acceleration  = 4m/s²

Unknown:

Mass of the rock  = ?

Solution:

According to newton's second law of motion;

           Force  = mass x acceleration

Insert the given parameters to find the mass;

         28  = mass x 4

             mass  =   = 7kg

the answer is b i think

a lot of it means it can be "burned" for energy and sold at one price. if it is scarce, the price will go up