Emma is working in a shoe test lab measuring the coefficient of friction for tennis shoes on a variety of surfaces. The shoes are pushed against the surface with a force of 400 N, and a sample of the surface material is then pulled out from under the shoe by a machine. The machine pulls with a force of 300 N before the material begins to slide. When the material is sliding, the machine has to pull with a force of only 200 N to keep the material moving.

a. What is the coefficient of static friction between the shoe and the material?

Question

Physics

London

12 November, 07:12

Emma is working in a shoe test lab measuring the coefficient of friction for tennis shoes on a variety of surfaces. The shoes are pushed against the surface with a force of 400 N, and a sample of the surface material is then pulled out from under the shoe by a machine. The machine pulls with a force of 300 N before the material begins to slide. When the material is sliding, the machine has to pull with a force of only 200 N to keep the material moving.

a. What is the coefficient of static friction between the shoe and the material?

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Answers (1)

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Liliana Davenport · Answer 1

normal force in the vertical direction = 400 N

static friction = 300

uS*N = 300

uS * 400 = 300

us = 0.75

dynamic friction or kinetic friction = 200

uK * 400 = 200

uk = 0.5

a) 0.75 b) 0.5