physics- multiple choice

1. Two forces are applied to a box on a frictionless surface. One force is 40 N [S]. The second force is 70 N [N30ºW]. What is the overall net force?

a) 40.6 N [S59.5ºE]
b) 110 N
c) 40.6 N [N59.5ºW]
d) 40.6 N [S30.5ºW]

2. When drawing free body diagrapms, it is important to:

a) draw your diagram to scale
b) add force vectors tip-to-tail
c) represent the magnitude force using the length of the arrows
d) all of the above

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  1. a. one force is south, the other is slightly north of west. Well, the resultant definitely is towards the west, which eliminates a, b.

    So what is the N component of the second force Northcomponent=70sin30 = 35Newtons, but there is a 40N S force, so the net force is S of W

    b. silly question,when drawing one never has it to scale, only approximately so. tip to tail is important.
    what about magnitude? well it helps, but we always just sketch.

    So b is the best answer, but I can see a poorly prepared teacher ready to argue. Don't argue with the teacher, it is a losing battle, usually, in Physics classes.

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