Problem

A suitcase of weight Mg = 450. N is being pulled by a small strap across a level floor. Th...

A suitcase of weight Mg = 450. N is being pulled by a small strap across a level floor. The coefficient of kinetic friction between the suitcase and the floor is µk = 0.640.

a) Find the optimal angle of the strap above the horizontal. (The optimal angle minimizes the force necessary to pull the suitcase at constant speed.)

b) Find the minimum tension in the strap needed to pull the suitcase at constant speed.

Step-by-Step Solution

Solution 1

Step #1 of 8

Think:

By drawing a free body diagram of the system, and on applying Newton’s second law, this problem can be solved.

Step #2 of 8

Research:

Identify the forces acting on the suitcase. The frictional force will be directed in a opposite direction to the motion of the suit case. The forces on the suitcase along the x axis are the frictional force and the x component of the tension force in the strap and the forces on the suitcase along the y axis are the normal force, gravitational force and the y component of the tension force in the strap.

Step #3 of 8

Sketch:

The free body diagram for the suitcase is shown below,