# Distance amplifiers

1. Sep 9, 2006

### jlee

Question: Just as there are block & tackle that amplify weight handling, for example, a man pulls down on a rope with 10 lbs of force and lifts 100 lbs as a result: Are there mechanical devices that amplify distance? E.G. a man moves down a 100 lbs weight 4 feet and thereby moves upward a 10 lbs weight 8 feet or 10 feet or 12 feet, etc. The block & tackle system sacrifices distance for weight amplification. The distance amplifier sacrifices weight for increased distance?
Anything in classical mechanics or Newtonian physics that has been overlooked?

2. Sep 9, 2006

### Gokul43201

Staff Emeritus
The lever: Put the fulcrum nearer the end of the effort arm. You get a mechanical advantage < 1, but a velocity ratio > 1.

Gears: Ever ridden a multiple gear bicycle on a high gear ratio?

3. Sep 9, 2006

### Staff: Mentor

Or take your block and tackle and swap the ropes that the man and the load are attached to.

4. Sep 10, 2006

### tim_lou

in all cases, energy is conserved...
$$F_1d_1=F_2d_2$$

5. Sep 11, 2006

### HallsofIvy

Staff Emeritus
In a sense, the same block and tackle (lever and fulcrum, screw, ramp, i.e. all simple machines) that "amplify" force also "amplify" distance. Unfortunately, because energy= force*distance is conserved to do one, you have to "undo" the other. If I hoist a weight using a block and tackle with n "lines", I only have to apply force equal to 1/n times the weight but I only lift it 1/n times the distance I pull. If I attach the weight to the end I was pulling on and go pull on the other end (what jtbell said), I reverse that: I lift the weight n times the distance I pull, but I have to apply n times the weight in force.

Similarly, as Gokul43201 said, using a lever "the wrong way around" will "amplify" distance moved at the cost of using addtional force.

6. Sep 11, 2006

### Danger

This is also the basis of most hydraulics in heavy construction equipment, the 'Jaws of Life' and other such devices. The cylinder might have a stroke of only a foot or so, but moves the load 10 feet. Hydraulics have such enormous force that the trade-off is acceptible.