Static Friction & Kinetic Friction

[ariol]

Problem 1: You need to move a 125-kg piece of furniture in your living room. You and your friend exert a force of 305 N to start it moving. What is the coefficient of static friction between the furniture and the floor?

Problem 2: A 20-kg bowling ball slides half way down a lane with a acceleration of 3.3 m/s^2before it starts to roll. What is the coefficient of kinetic friction between the ball and the lane that is starts rolling?

 

[arildno]

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[nlightner]

I would approach these problems by first understanding the concept of friction. Friction is a force that resists the motion between two surfaces in contact with each other. It can be divided into two types: static friction and kinetic friction.

Static friction is the force that must be overcome in order to start an object in motion. Once the object is in motion, kinetic friction comes into play, which is the force that opposes the ongoing motion of the object. The coefficient of friction is a measure of the amount of friction between two surfaces and is denoted by the symbol "μ."

In problem 1, we know that the force exerted by you and your friend is 305 N and the mass of the furniture is 125 kg. Using Newton's second law of motion (F = ma), we can calculate the force required to overcome the static friction and start the furniture in motion. This force would be equal to the product of the mass and the acceleration, which is 125 kg * 305 N = 38125 N. Since this force is equal to the maximum static friction, we can use the formula μ = F/N (where F is the force required to overcome static friction and N is the normal force between the two surfaces) to calculate the coefficient of static friction. Thus, μ = 38125 N/305 N = 125/1 = 0.24. Therefore, the coefficient of static friction between the furniture and the floor is 0.24.

In problem 2, we know that the bowling ball has a mass of 20 kg and an acceleration of 3.3 m/s^2. Using Newton's second law, we can calculate the force required to overcome the kinetic friction and start the ball rolling. This force would be equal to the product of the mass and the acceleration, which is 20 kg * 3.3 m/s^2 = 66 N. We also know that the normal force between the ball and the lane is equal to the weight of the ball, which is 20 kg * 9.8 m/s^2 = 196 N. Using the formula μ = F/N, we can calculate the coefficient of kinetic friction as μ = 66 N/196 N = 0.34. Therefore, the coefficient of kinetic friction between the ball and the lane is 0.34.

In conclusion, understanding the concepts of static and kinetic friction and using the appropriate formulas can help