# I am totally lost

1. Sep 10, 2004

### chopster

I am totally lost!!

I am taking this math class and we are now doing these statics problems and I have no clue what is going on, as I have never taken a physics class. I was hoping if someone could just explain on how I can put these two word problems into a equation because I have no problem with the math portion or it, I just have a hard time understanding word problems. Anyway if anyone can help me I will greatly be appreciated.

The first problem is,

A horizontal bar of negliglible weight hangs from two cables, one at each end. When a 624-N force is applied vertically downward from a point 185 cm from the left end of the bar, the right cable is seen to have a tension of 341 N. find the length of the bar.

One of the main problems is I have no clue what the N stands for or to even start, my book has one example and it is no where the same type of problem that it shows.

The second problem is,

A uniform horizontal beam is 19.80 ft long and weighs 1360 lb. It is supported at either end. A vertical load of 13,510 lb is applied to the beam 8.450 ft from the left end. Find the reaction at each end of the beam.

Again I don't what to do, I just need a explanation or if someone knows of a tutorial or sample problem to help me answer these two problems. Like I said I have no problem with the math portion it is extraction the word problem into an equation to solve the problem.

Any info will greatly be appreciated.

Thanks Chris

2. Sep 10, 2004

### Sirus

To begin, N is newtons, a unit of force. For the first problem, find the tension in the left cable, then establish a ratio between the two, and use this same ratio for lengths to find the total length of the bar. I think this should work. The second problem should be solved in a similar manner.

3. Sep 11, 2004

### chopster

Thanks for the reply Sirus, I believe I got the first one so I was wondering if you could check it out.

(341*x)/624=185

x=339

Now I just need to figure the second one out because I just don't get the finding for both side of the question!! :yuck:

Again I appreciate the reply, I just cannot wait until I am done with these word problems.

4. Sep 11, 2004

### arildno

For your second problem:
You've got 2 unknowns; the reaction forces on each end.
Since the beam is in (static) equilibrium, Newton's 2.law of motion requires that the sum of external forces acting on the beam must equal 0.
You also need that the sum of torques (about a point) is 0 in order to have static equilibrium.
So, first steps:
Make a list of external forces acting on the beam, and where they act.
Choose a point to compute the torques about.

5. Sep 11, 2004

### chopster

Okay I think I got it but I was wondering if someone could check it and see if it is right.

(1360 * 9.9) + (13510 * 8.45) = x * 19.8

x = 6445 lb

1360+13510=x+6445

x = 8425

Thanks again for all the help

6. Sep 11, 2004

### arildno

chopster:
It is just about impossible to verify whether a bunch of numbers is correctly heaped together.
Please use clear labels on the quantities rather than their numerical values.

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