Question

Question: When an object is pushed several ways at once, what is the net effect? In mechanics, we think of "force" as a push or a pull. A scientific definition will be discussed later in lecture, and the effects that forces produce on motion will be a major topic of this course. The unit of force in the SI system is the Newton (abbreviation N). For purposes of this exercise, we will be concerned with the way that different forces combine to produce a total force. Part P-1: North Force of wind on sails Example - A sailboat in a lake is pushed northeast by the wind and east by the lake current, as in Figure 1. These forces are indicated in the figure with arrows. The total force on the boat will be directed somewhere between these two. In fact, we can find exactly what is the effect of the combined forcesFigure 1: Two forces on a sailboat: Note that the two by a technique shown in Figure 2. forces are drawn from a common point. East Force of current on boat In Figure 2 we have drawn a parallelogram whose sides are parallel to the two forces. The diagonal of this parallelogram (drawn from the same common point) is the total force acting on the boat. The length of the vector represents the total amount of force (magnitude) on the boat and the direction the vector points is the direction of that total force. Whenever two forces act on the same object, the total force can be found this way. The total force is sometimes called the resultant of the other two. Using a ruler and a protractor draw a vector diagram, like the one shown in Figure 2. Figure 2 will help you find the resultant force on the boat by the parallelogram method. total force on boat For this problem use the following information: now the wind pushes the boat with a force of 50ON at an angle of Figure 2: Finding the total force on the sailboat by the parallelogram method 60° north of east while the current pushes the boat with a force of 300N at an angle of 45° south of east. First pick a scale for the length of the vectors to adequately represent the forces given. Your scale should be set up so that the vector diagram takes up most of the graph paper. Be sure to write your scale (with units!) on the diagram and label the vectors. Last Revised 07/17/2015 Force Vectors

Answer 1

(a) Resultant magnitude is approximately 10.25 units = 10.25 x 50 = 512.5 N

(b) Direction is approximately 25.5° north of east.

Worlh Scale 1:50 N Force of ind ón boat 10.2s unit Resulda imi 25.5 45 70.5 Eost orte af current on bent