Question

You have to move your 100 N couch before a delivery company drops off your new one. Unfortunately your roommate is passed out on it. The coefficient of friction between the couch and floor is .43. It takes 250 N of force to get the couch moving. a) How much does your roommate weigh in Newton’s? b) After you get the couch moving it only takes 200 N to keep it moving at a constant speed, what is the coefficient of kinetic friction?

Answer 1

Answer:

a) Weight of Roommate = 481.4 N

b) μk = 0.34

Explanation:

a)

The force required to move the couch must be equal to the force of friction:

F = frictional force

F = μW

W = F/μ

where,

W = Total Weight of Couch and Roommate

F = Force Required start to move couch = 250 N

μ = coefficient of static friction between couch and floor = 0.43

Therefore,

$W = \frac{250 N}{0.43}\\\\W = 581.4 N$

So, the total weight is given as:

W = Weight of Couch + Weight of Roommate

Weight of Roommate = W - Weight of Couch

Weight of Roommate = 581.4 N - 100 N

Weight of Roommate = 481.4 N

b)

Now, the force required to keep the couch moving can be given as equal to the kinetic friction force:

F = kinetic friction

F = μk*W

μk = F/W

where,

μk = coefficient of kinetic friction = ?

F = Force required to keep the couch moving = 200 N

Therefore,

μk = 200 N/581.4 N

μk = 0.34