Question

A flight attendant pulls her 75.8 N flight bag
a distance of 256 m along a level airport floor
at a constant velocity. The force she exerts is
47.0 N at an angle of 62.4◦
above the horizontal.
a) Find the work she does on the flight bag.
Answer in units of J
b) Find the work done by the force of friction
on the flight bag.
c) Find the coefficient of kinetic friction between
the flight bag and the floor.

I am very confused about how to find the coefficient of kinetic friction. A step by step would be very helpful. Thanks!

Answer 1

You are given in this problem the force that the flight attendant is exerting on the bag. You are also given the mass of the bag.

What you need is the coeff. of friction. The equation for that is as follows:

F = u N ; 'u' is the coeff. of friction and 'N' is the normal force.

What you need to do is find out what F and N are.


N is the normal force. This is the force of the floor pushing up on the bag. So what you need to do is calculate the weight of the bag (mg). Then you need to calculate the component of the flight attendant's force that is acting vertically. The difference between these two forces is the net force acting downward on the floor and, hence, the normal force acting upwards on the bag.

F is the horizontal component of the flight attendant's force. It's the one you didn't use in the previous calculation of N.

Simply do F/N to find u.