Lesson 4 of 15
Two at once
Show on a big screenTwo teams pull a rope. Which team wins?
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Step 1 of 3
- One rope pulls left with 30 N. Leftover: 30 N left.
- A second rope pulls right with 18 N. Leftover: 12 N left.
- A third rope pulls right with 16 N. Leftover: 4 N right.
The rule
With only these pulls, the object moves toward the bigger side.
Forces on one line, the same way, add. Forces on one line, opposite ways, subtract. What is left is the net force. It has a size and a direction.
Step 2: 30 N − 18 N = 12 N left. In step 3, the right pulls add. 18 N + 16 N = 34 N. Then 34 N − 30 N = 4 N, to the right. The net force now points right.
Try the lab to finish this lesson.