Understanding Spring Forces: Net Force and Spring Scale Readings

[turdferguson]

I just want to quickly check something. A spring scale lies horizontally on a frictionless surface. A horizontal force of 10 N to the right is applied to the top of the scale and another horizontal force of 10 N to the left is applied to the bottom.

1. The net force is ___ obviously 20 N

2. The reading on the spring scale will read ___ I am inclined to think that it would only be 10 N. The situation would be the same if the spring was attached to a wall. Am I right? Afterall, they wouldn't ask the same question twice

 

[Doc Al]

1. The net force is ___ obviously 20 N

This is incorrect. Rethink this: what's the net force on the spring scale? Recall that forces are vectors--direction counts.

2. The reading on the spring scale will read ___ I am inclined to think that it would only be 10 N. The situation would be the same if the spring was attached to a wall. Am I right?

Yes, you are right. The spring scale reads the tension in the spring, which is 10 N.

 

[ponjavic]

This is incorrect. Rethink this: what's the net force on the spring scale? Recall that forces are vectors--direction counts.


Yes, you are right. The spring scale reads the tension in the spring, which is 10 N.

I saw this question before and it got me thinking, I do not really understand it. The spring is being compressed by two forces. Now if the reading is based on the fact that two equal and opposite forces will always act on the spring and then it takes the size of these forces that is okay.

I still cannot seem to get over the fact that there are two 10N forces compressing the spring.

 

[Doc Al]

I still cannot seem to get over the fact that there are two 10N forces compressing the spring.

If you can figure out a way to compress (or stretch) a spring by pushing (or pulling) on one end only, I'd like to see it. (Won't happen!)

The spring scale measures the degree of compression (or elongation) which is proportional to the compression force (or stretching force).

 

[ponjavic]

If you can figure out a way to compress (or stretch) a spring by pushing (or pulling) on one end only, I'd like to see it. (Won't happen!)

The spring scale measures the degree of compression (or elongation) which is proportional to the compression force (or stretching force).

That's actually what I was trying to do :D