A 100 N box is initially at rest on a rough surface. The coefficient of static f
ID: 1525909 • Letter: A
Question
A 100 N box is initially at rest on a rough surface. The coefficient of static friction is 0.6; the coefficient of kinetic friction is 0.4. A constant 35 N force directed to the right is applied to the box. Some students discuss the frictional force exerted on the box by the rough surface 1 second after the force is first applied
Alice: “The frictional force is 60 N since the box will not be moving and the
coefficient of static friction is 0.6 with a normal force of 100 N.”
Bob: “The frictional force is 40 N since the coefficient of static friction is 0.4
and there is a normal force of 100 N.”
Carlo: “The frictional force is 35 N since the box will not be moving and the
frictional force will cancel out the applied force of 35 N.”
David: “The normal force is 100 N and the coefficient of kinetic friction is
0.4, resulting in a kinetic frictional force of 40 N. Similarly static
Friction is 60 N, since the coefficient of static friction is 0.6”
Who do you agree with? Explain your reasoning.
Alice ___ Bob ___ Carlo ___ David ___ None of them ___
Explanation / Answer
David: “The normal force is 100 N and the coefficient of kinetic friction is
0.4, resulting in a kinetic frictional force of 40 N. Similarly static
Friction is 60 N, since the coefficient of static friction is 0.6”
in fact the box will not move. Because the applied force is not enough to overcome the friction. David explained the frictional forces acts on the box.
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