What would the scale read?

Question

Two 10 N weights are attached to a spring scale as shown below. Does the scale read 0, 10, 20 N, or any other reading?

(Would it read any differently if one of the ropes were tied to the wall instead of to a hanging 10 N weight?)


http://img158.imageshack.us/img158/7272/hw3zu.jpg

Answer 1

I took college physics my freshman year and we went over this problem a lot, and it may seem confusing but the answer is only 10N! Please look at this website i found to verify.

Here's why: The scale is measuring TENSION in the string. When you hold the scale and just put one block on, it will read 10N because that is the amount of tension in the one string. If you add a second string with a second mass like in your question, that string will also have a tension of 10N from the block. Each string has a tension of 10N, so that is what the scale reads.

If you removed the scale, and just had one string what do you think would be the tension in that one string. Think about it by drawing free body diagrams. (Always very important!!) What are the forces on each block? Gravity and tension. Since the block is not accelerating, gravity must be equal and opposite to tension. So since gravity is 10N, tension is 10N. If tension was 20N, then the blocks would accelerate in the opposite direction gravity is pulling. The scale cannot read zero because that would mean there is zero tension. There is tension in the string because gravity acts on the blocks.

Answer 2

I am not 100% but I think 20 N this way and 10N if one end to the wall. Reason is that there is a total gravitationally caused force on the scale of 20 N. One from either side of the scale. With the wall, the wall is exerting a force of 10 N against and the weight is exerting a force of 10 N ON the scale. The wall scenario is easy, it is like holding the scale vertically and the mass of the weight will read on the scale as we would expect. BUT ADDING 10 N to the TENSION in the spring, would sum the masses. It would be like an instantaneous reading if you were to hang 10N on the scale and JERK UPWARDS on the scale, the scale WILL move. If you applied EXACTLY 10 N of "JERK" the scale would temporarily/instantaneously - at the top end - be a total of 20N.

Answer 3

The scale will read only 10 newton.
This is the same as if one rope is tied to a wall.

When one rope is tied to a wall the balance will read 10N.

Instead if tieing the rope we have attacehed equal weight, that is equivalent to the upward pull when hung in the wall.

Answer 4

It would read 20N. If you consider resolving the forces at every point [remembering that the tension in a rope is the same at every poitn] this is the only reasonable answer. If you fix one weight the scale would read 10N for a similar reason.

Answer 5

I'm 100% certain it would show 20 N. The two vector forces would combine.

Answer 6

it would read 20N in normal condition. but if one rope is tied towall then it would show 10N.

Answer 7

or it could be in kilograms - 82.0 kilograms = 180.4 lbs... multiply kilograms by 2.2 Or it needs new batteries or is defective. Unless you really weight 82 lbs.

Answer 8

0? how can you think this late. I'm guessing