PhysicsBowl 2019 Q43

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PhysicsBowl 2019

43) For question 43, we need to find the coefficient of static friction between the two boxes. We can start by drawing out the force diagram.

Where f is frictional force, F is applied force, and m is mass

Since Newton's third law tells us that the frictional forces f[1on2] and f[2on1] are equal and opposite forces, the net force will be F. We can use Newton's second law to find the net acceleration.

Where F is force, m is mass, and a[sys] is the net acceleration of the system

Keep in mind that the problem specifies that box 1 does not slip on box 2, which tells us that both boxes move with the same acceleration.

Next, if we look at the forces acting on block 1, the only force is f[2on1]. Using Newton's second law for the net force, and the general form for frictional force, we can solve for the friction coefficient.

Where m is mass, a[sys] is the net acceleration of the system, f is frictional force, μ is the friction coefficient, N is normal force, and g is acceleration due to gravity

Answer: A