Question

Mazie stands on her kitchen floor. The coefficient of kinetic friction between her socks and the floor is 0.62, and the coefficient of static friction is 0.75. She has a mass of 42 kg.

a. What is the maximum force of static friction between her socks and the floor?


b. If you push Mazie with a force of 350 N, will she start to slide? Explain your answer.


c. Mazie slides across the floor at a speed of 0.6 m/s. What is the force of kinetic friction acting on her?

Answer 1

a) It equals the force required to make her start moving: F.max=0.75*42*9.8=308.7 N

b) Yes, cause 350 newtons force will 'overcome' static friction force.

c) F=mgk=42*9.8*0.62=255.19 N

Answer 2

Okay so static friction is when the atoms lock themselves into place, which makes it 'hard' to push until you exceed its static force.

You can calculate the Fs by finding your normal force and multiplying it by your static friction force.

N = mg = (9.8)(42) = 411.6 N

Fs = NKs = (411.6)(0.75) = 308.7

a) the maximum force of static friction between her socks and the floor is 308.7 N

b) If you push Mazie with a force of 350 she will slide. She will accelerate if you keep pushing her with the constant force, but if you push her and let go the kinetic friction will eventually bring her to a stop.

c) So this is an interesting question, she's going at a speed of 0.6 m/s. Kinetic friction is pushing her back so theres a negative force which is the force of kinetic friction right. So its NKf = (411.6)(0.62) = 255.192.