Force vs. Time on a Dynamics Cart (10:45)
When the forces in a free body diagram don’t change students often think that Newton’s Second Law will yield the same results.  This demonstration shows that is not true.  This is a step-by-step analysis of tension force as a function of time for a dynamics cart in motion on a horizontal track.

Content Times:
0:13 Reviewing known information
0:47 The three parts in this demonstration
1:22 Drawing the two free body diagrams
2:27 Understanding the free body diagrams
3:12 Identifying the String Direction
4:08 Finding the Tension Force during Part #1
6:06 Theoretical vs. Experimental Tension Force during Part #1
6:28 Finding the Tension Force during Part #2
7:52 Theoretical vs. Experimental Tension Force during Part #2
8:13 Finding the Maximum Acceleration during Part #3
9:37 Instantaneous vs. Average
10:21 All the graphs sequentially

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