Force and Acceleration Test Review

# The coefficients of friction between a passenger and

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The coefficients of friction between a passenger and the seat are μ s = 0.5 and μ k = 0.3. Will a 70 kg passenger slide off the seat if not wearing a seatbelt? NO… static friction can handle a maximum acceleration of 4.9m/s s . 3) A horizontal force of 12,500 N acts for 5 s on a 2,150 kg car which is starting from rest. The car then slams on the brakes and skids to a stop over 40 m, what is the coefficient of kinetic friction between the tires and the road? μ=1.08 4) A 5 kg book is being pushed against a vertical wall which an unknown horizontal force. The coefficient of static friction between the wall and the book is 0.4. What is the minimum horizontal force needed to prevent the book from sliding down the wall? 122.5 N What would happen to the force of friction if you doubled the horizontal force applied to the book? You tell me… 5) Santa parked his sleigh 5 m from the edge of a 20° roof. Unfortunately, the parking brake failed. If the μ k = 0.08 between the roof and the sled, what will the sled’s velocity be the moment before it goes over the edge? 5.11 m/s I wonder if this could turn into a projectile problem… 6) Assuming no friction, how long will it 7) What will the final velocity of the 8 kg mass be take for the 7 kg mass to fall 0.5 m? after 3s? Assuming starting from rest and μ k =0.2 Assume starting from rest. 0.45s 0.75 m/s 40° 3kg 7kg

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• Fall '11
• Hill

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