# Feedback Q&A on Machines

by Ron Kurtus

Readers have sent in a total of 14 comments and questions on Machine issues. They are listed according to date.

You can read them to further your understanding of the subject.

## List of next 10 letters

### Country

Machines Using levers in health care Ghana

Levers Lifting 250 pound log with a crowbar USA

Machines Centrifugal acceleration in sieving machine South Africa

Pulleys Wants equations for complex pulley system USA

Next 10

First 10 letters

## Using levers in health care

Topic: Machines

### Question

March 13, 2010

How does levers applied in health care provition?

abednego - Ghana

19364

### Answer

There are many devices using levers in health care. The brake on a wheelchair uses a lever. Levers are used to adjust the level and inclination of a hospital bed. Levers are sometimes used to life heavy hospital equipment.

I am sure if you would be observant and look around where health care is being provided, you will see other examples of levers being used.

Back to top

## Lifting 250 pound log with a crowbar

Topic: Levers

### Question

January 18, 2010

This is embarrassing. I am sorry. High School was 30 years ago.
I have a 250 pound log. I have an 8 ft crow bar.

Where must I put that crow bar (fulcrum underneath) so that I only have to push down 70 pounds. I know the closer u are to the ebject the more u can lift. Please give me real numbers. I knowu cross multipy - like ur formulas suggest.

I saw firewood - logs into 21 inches. 200 year old tree 21 in long, weights 150 - 200 or more pounds.

Thank you

RipSaw - USA

19074

### Answer

You shouldn't be embarrassed, because it is not a straightforward solution.

Let x be the distance from the 250 lb weight to the fulcrum. Then 8 - x is the distance to the 70 lb weight.

250x = 70(8 - x)
250x = 560 - 70x
320x = 560
x = 1.75 ft from the 250 lb weight.

For more information on levers, see:
http://www.school-for-champions.com/science/machines_lever.htm

Back to top

## Centrifugal acceleration in sieving machine

Topic: Machines

### Question

January 18, 2010

"the machine works best when the resulting centrifugal acceleration comes up to the value of 20m/sec squared"

Quote from sieving machine manufacturer comments of the working of machine.

What exactly does this mean ?

Brian - South Africa

19073

### Answer

When something spins, it creates a centrifugal force, pulling objects outward. Since force is related to acceleration (F = ma), you could call it centrifugal acceleration, although you should also know the radius of the object.

The sieving machine probably requires a rotation speed to create the acceleration and force to push objects to the outside wall.

Back to top

## Wants equations for complex pulley system

Topic: Pulleys

### Question

December 17, 2009

I'm a firefighter doing technical rescue work. We use a double rope system (2 ropes, one mainline, one belay or safety back up rope,no load on it). The question is the load transferred to the belay rope in the event of a failure of the mainline rope. the mainline rope carries all the weight of the rescue, while the belay or safety carries none. I can't seems to find one formula to get an answer regardless of the load(weight) on the rope. I now mass(load)is needed, & distance droped is important, & distance droped (should be a percent of gravity speed(32ft/s(s), but that plugs in where in which formula? 100Kg. rescue, fall 6ft, how much force(load,KG/Lbs) is transfered to the belay line. Or 250Kg rescue and patient falls 6ft. I feel this is important when teaching new rescue tech. the importance of the belay person, who controls the belay line(and will save the rescuer on the rope) at all time. The rope used is a "static" rope, no stretch per say. All the components(pulleys,rope,webbing,carabiners) of the mainline/belay line are rated for only so much force(kg/lbs.), once exceeded you will run the risk of failure of the entire system. Thanks for your/any help in what must seem like a simply question.

gregory - USA

18866

### Answer

I'm sorry but we don't have any information or equations on complex pulley systems. It is difficult to even visualize your system unless familiar with it. I would think some rescue textbooks would have some details on it.

Best wishes in finding your answer.

Back to top

Next 10

## Summary

Hopefully, this reader feedback has helped provide information about Machine issues.

Always do your best

## Resources and references

Ron Kurtus' Credentials

Resources

## Questions and comments

Do you have any questions, comments, or opinions on this subject? If so, send an email with your feedback. I will try to get back to you as soon as possible.

Feel free to establish a link from your website to pages in this site.

## Where are you now?

School for Champions

Machines

## Also see

### Let's make the world a better place

Be the best that you can be.

Use your knowledge and skills to help others succeed.

Don't be wasteful; protect our environment.

### Live Your Life as a Champion:

Take care of your health

Seek knowledge and gain skills

Do excellent work

Be valuable to others

Have utmost character

#### Be a Champion!

The School for Champions helps you become the type of person who can be called a Champion.