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# Why do longer elastic bands have less resistance? Watch

1. As the title says? Longer elastic bands are easier to stretch than the shorter ones. Cheers
2. For the same force, they will stretch by the same fraction. However, given they are longer you can stretch them by the same length with a lower force.
3. Extending a 5cm band by, say, 1cm involves a strain of 1/5 = 0.2
Extending a band of 10cm by 1 cm involves a strain of 1/10 = 0.1 [half the amount]
Strain is extension divided by original length.
As the force required depends on the strain [Stress = Young Modulus x strain] then for the longer band you require less force (stress). This assumes the bands have the same elastic modulus.
4. (Original post by Stonebridge)
Extending a 5cm band by, say, 1cm involves a strain of 1/5 = 0.2
Extending a band of 10cm by 1 cm involves a strain of 1/10 = 0.1 [half the amount]
Strain is extension divided by original length.
As the force required depends on the strain [Stress = Young Modulus x strain] then for the longer band you require less force (stress). This assumes the bands have the same elastic modulus.
Thank you very much! My results from my experiment show that the longer elastic bands snapped under less force. This must purely be because the material properties of the longer elastic bands are different to the shorter ones? Is there an explanation why the bonds are weaker in the longer bands? Are they stretched in manufacturing or cut from the same material? Cheers
5. I'll rephrase, do longer elastic bands therefore require more force to break?
6. (Original post by TableChair)
For the same force, they will stretch by the same fraction. However, given they are longer you can stretch them by the same length with a lower force.
Do longer elastic bands therefore require more force to break?
7. No, the tensile strength is the same (the stress required to break it). Note stress does not depend on length but only on cross-sectional area and the applied load.

Without being able to see the elastic bands or knowing anything about their manufacture, I can't really comment on why your experiment produced such results. Are you sure it is a definite trend and not just random variation? Presumably they have the same cross-sectional area?
8. (Original post by KungFuChicken)
Thank you very much! My results from my experiment show that the longer elastic bands snapped under less force. This must purely be because the material properties of the longer elastic bands are different to the shorter ones? Is there an explanation why the bonds are weaker in the longer bands? Are they stretched in manufacturing or cut from the same material? Cheers
I'm not sure.
It's not just "force" that snaps the bands, it's stress. Stress is force divided by cross section area; and the bands, as they stretch, also narrow.
This will cause a greater stress for the same force.
So the thickness is also important.
You may find some more info on the net if you Google it. There should be plenty of stuff out there on the elastic properties of rubber.

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