Solving Newton's First Law: Spider Attached to Two Threads

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A spider attached to two equal-length threads forming a 120-degree angle is analyzed under Newton's First Law, which states that the sum of forces must equal zero. The spider's mass is given as 30 mg, leading to a downward force of -3.0 * 10^-4 N. The tension in each thread is initially calculated as T1 = 1.5 * 10^-4 N, but the correct tension is confirmed to be 3.0 * 10^-4 N for each thread. The confusion arises from the vector nature of forces, emphasizing the need to consider both magnitude and direction in calculations. Understanding the vector components is crucial for resolving the forces accurately.
brad sue
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Please ,
Explain me this situation
A spider is attached to two threads of equal length that make a 120o angle with each other. The spider is motionless and its mass is m=30mg.
What is the tension in each thread?

According to the Newton first Law, the sum of the force must be 0.

T1+T2+Fspider=0
since the threads are the same length and symetrical, T1=T2.

Fspider=-3.0 *10-4N

so I found T1=1.5 *10-4N

I am surprised to see that the answer is 3.0 *10-4N on each thread

please now I am confused! help
 
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Forces are vectors...
 
Hurkyl said:
Forces are vectors...
ok but how it is help me please?
 

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