Rotational Motion - Self Test

Solution to Question 1: The Right Hand Rule

Recall that  = r x F, (or  = r F sin) and that the Right Hand Rule says that the thumb points into the direction of torque  when the fingers curl in the direction of the cross product (ie. from r to F). Furthermore, the symbol  represents a vector going into the screen, while  is a vector pointing out of the screen.
Part a

Figure 1 Diagram for Question 1, first problem
In the first problem, you would point your fingers in the direction of r (left-ward), and 'curl' them upwards (into the direction of F). Your thumb should point into the screen. (Be sure you are using your right hand.) 
Part b

Figure 2 Diagram from Question 1, second problem
In the second problem, r points to the right, so point your fingers to the right. Now 'curl' them upwards, in the direction of F. Your thumb should point out of the screen.


Explanation on Torque (including the Right Hand Rule)
Example Problem on the Right Hand Rule
Continue to: Question 2: Definition of Torque
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