Forces and the Laws of Motion

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Forces and the Laws of Motion

Problem D

COEFFICIENTS OF FRICTION PROBLEMs

1. If the coefficient of kinetic friction between a 11 kg object and the ground is 0.39, what is the magnitude of the frictional force that must be overcome?

2. Robert Galstyan, pulled two coupled railway wagons a distance of 7 m. The total mass of the wagons was about 2.20 ´ 105 kg. Suppose the wheels are blocked and the coefficient of static friction between the rails and the sliding wheels is 0.220. What would be the magnitude of the minimum force needed to move the wagons from rest? Assume that the track is horizontal.

3. Suppose a force of 1.13 ´ 108 N is needed to overcome static friction in a train’s wheels. If the coefficient of static friction is 0.741, what is the train’s mass?

4. A blue whale with a mass of 1.90 ´ 105 kg was caught in 1947. What is the magnitude of the minimum force needed to move the whale along a horizontal ramp if the coefficient of static friction between the ramp’s surface and the whale is 0.460?

5. Suppose that a car’s brakes are suddenly applied and the car slides to a stop. If the force required to stop the car is 6.0 ´ 103 N and the coefficient of kinetic friction between the tires and pavement is 0.77, what is the magnitude of the car’s normal force? What is the car’s mass?

6. Suppose Brian Newton drags a bag with an applied horizontal force of 130 N, so that the bag has a net acceleration of 1.00 m/s2. If the coefficient of kinetic friction between the bag and the pavement is 0.158, what is the mass of the bag of coal?

7. Cleopatra’s Needle, an obelisk given by the Egyptian government to Great Britain in the nineteenth century, is 20+ m tall and has a mass of about 1.89 ´ 105 kg. Suppose the monument is lowered onto its side and dragged horizontally to a new location. An applied force of 7.6 ´ 105 N is exerted on the monument, so that its net acceleration is 0.11 m/s2. What is the magnitude of the frictional force?

8. A ship launched from a dry-dock slides into the water at a constant velocity. Suppose the force of gravity that pulls the ship downward along the dry-dock is 4.26 × 107 N. If the coefficient of kinetic friction between the ship’s hull and the dry-dock is 0.25, what is the magnitude of the normal force that the dry-dock exerts on the ship’s hull?

9. A passenger with a mass of 60.0 kg is standing in a subway car that is accelerating at 3.70 m/s2. If the coefficient of static friction between the passenger’s shoes and the car floor is 0.455, will the passenger be able to stand without sliding?

10. A dogsled with a mass of 47 kg is loaded with 33 kg of supplies. If the coefficient of kinetic friction between the sled’s runners and the snow is 0.075, what is the magnitude of the frictional force on the sled as it moves across flat ground?

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Holt Physics 39 Problem Workbook