PhysicsBowl 2017 Q25

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PhysicsBowl 2017

25) This question asks us to find the coefficient of kinetic friction between the block and the incline in the problem above. We can start by drawing out the conditions at the bottom and top of the incline.

Where ℓ is length, v is velocity, and h is height

We used sine trigonometry to find that ℓ, the length, is 5.2 meters.

Next, we can use the conservation of energy to solve for the frictional force. Remember that there is work done by friction that is accounted for in the conservation of energy.

Where m is mass, v is velocity, g is acceleration due to gravity, h is height, f is frictional force, and ℓ is length

After this, if we expand the frictional force we can solve for the friction coefficient and cancel out mass.

Where m is mass, v is velocity, g is acceleration due to gravity, h is height, f is frictional force, ℓ is length, μ[k] is coefficient of static friction, N is normal force, and θ is the ramp's angle of elevation

Answer: B