Take into account that the Newton Second law is given by the following formula:
F = m·a
if you solve the previous formula for a, you obtain:
a = (1/m)·F
In the graph, you can notice that acceleration a is function of force F, just as in the previous formulation. The slope of the lines of the graph is 1/m, where m is the mass.
As you can notice in the formula for a, if m is greater, the slope is smaller.
Then, the blue line belongs to the smallest mass, the gray line belongs to the greatest mass, and the orange line is the middle mass.
Hence, you have:
- blue line - 40 kg
- gray line - 200 kg
- orange line - 100 kg