In a laboratory experiment on friction, a 136- block resting on a rough horizontal table is pulled by a horizontal wire. The pull gradually increases until the block begins to move and continues to increase thereafter. the figure shows a graph of the friction force on this block as a function of the pull.
What would the graph look like if a 136 brick were placed on the box, and what would be the coefficients of friction be in that case?
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So, the question is what would the graph look like if the box would have twice the weight. Friction coefficients wouldn't change, but all the forces would double (static and kinetic friction).
So, the graph would be double the initial force for every point on the curve. (starts moving at 150 N, instead of 75 & dynamic friction of 100 N, instead of 50)