Learn what elastic potential energy means and how to calculate it.
Log in Lucky 8 years agoPosted 8 years ago. Direct link to Lucky's post “In the rubber band exampl...” In the rubber band example, is the heat dissipated as work is done stretching the rubber band, or as the rubber band is being unloaded? • (13 votes) codysetchfield 8 years agoPosted 8 years ago. Direct link to codysetchfield's post “I'm fairly new to this to...” I'm fairly new to this topic, but from past experience of doing this in 3rd grade, we used to stretch a rubber band really quickly, then put it to our upper lip (while it was still stretched.). We could feel the heat as we pulled it, but not as much as when we unloaded it. So mathematically, I can't tell you the answer, but from experimentation, it does produce heat when loaded. (33 votes) Kyle Delaney 8 years agoPosted 8 years ago. Direct link to Kyle Delaney's post “Exercise 2 is worded very...” Exercise 2 is worded very strangely. It sounds like 0.6m is just the distance the string gets pulled back when 300N is applied, which would imply a specific spring constant, so why does the question make it sound like the spring constant could be anything? Is 0.6m just the maximum limit to how far the bow can be pulled back? That should be stated more clearly. Also, wouldn't any spring constant greater than 500N/m also allow the archer to use his full strength? • (7 votes) Anoushka B. 7 years agoPosted 7 years ago. Direct link to Anoushka B.'s post “The way I understood it, ...” The way I understood it, 300N is his maximum strength. If he useed 250N and produced an extension of 0.6m, the spring constant would be different (in which case the bow would probably be made in a different shape or size or with a different material). (2 votes) Jay Khan 8 years agoPosted 8 years ago. Direct link to Jay Khan's post “In question 2C, 2 x U sho...” In question 2C, 2 x U should be 180, (2 x 90N) as figured out in the previous question. So how does 2 x U = 2.9? Someone please explain, thanks. • (6 votes) Anuj Suresh 6 years agoPosted 6 years ago. Direct link to Anuj Suresh's post “Dude it not 2.9. Its 2*90...” Dude it not 2.9. Its 2*90. The dot there is for multiplication (3 votes) Aibek Zhylkaidarov 8 years agoPosted 8 years ago. Direct link to Aibek Zhylkaidarov's post “Why in Exercise1 250J/spr...” Why in Exercise1 250J/spring = 1000J? ( solution) • (3 votes) Taylor Boone 8 years agoPosted 8 years ago. Direct link to Taylor Boone's post “There are four springs on...” There are four springs on the truck in exercise 1 (one per wheel.) The displacement given is the displacement of the entire truck, meaning each individual spring is compressed 0.1 m. The calculation done (PE=(0.5)(5*10^4)(0.1)^2) gives you the amount of energy stored in each individual spring. Therefor the total energy stored in all four springs is 250 J * 4 springs = 1000 J total. (7 votes) Sahil Dahiya 6 years agoPosted 6 years ago. Direct link to Sahil Dahiya's post “In question 3, why is the...” In question 3, why is the heat energy = stress * strain * volume, instead of stress* strain * volume * .5, or am I missing something? • (6 votes) Lucky 8 years agoPosted 8 years ago. Direct link to Lucky's post “In a stress-strain graph,...” In a stress-strain graph, is the stress plotted always (force applied) / (original cross-sectional area of material) or is it (force applied) / (cross-sectional area of material when that force is applied)? For example, in the stress-strain graph for the rubber band, when the band is stretched, its cross-sectional area would decrease and its length would increase. • (4 votes) MELVIN SAM 6 years agoPosted 6 years ago. Direct link to MELVIN SAM's post “prove how energy/volume =...” prove how energy/volume =1/2 stress.strain • (4 votes) Juan Eduardo Ynsil Alfaro 7 years agoPosted 7 years ago. Direct link to Juan Eduardo Ynsil Alfaro's post “In the extension vs force...” In the extension vs force graph, what if the force was always constant? (e.g. the weight of a ball pulling down a vertical spring). In the graph, it isn't and just keeps growing as the displacement grows. • (1 vote) Andrew M 7 years agoPosted 7 years ago. Direct link to Andrew M's post “If the force was constant...” If the force was constant, you wouldn't have a spring. That's not what springs do. (5 votes) Jacoub 6 years agoPosted 6 years ago. Direct link to Jacoub's post “i don't understand how ex...” i don't understand how exercise 3 went from 0.05N/mm^2 to 5 x 10^4 N/m^2. • (2 votes) Hafsa Kaja Moinudeen 8 years agoPosted 8 years ago. Direct link to Hafsa Kaja Moinudeen's post “Why do we multiply the vo...” Why do we multiply the volume of the rubber by the heat in the last exercise? • (2 votes) levgenid 8 years agoPosted 8 years ago. Direct link to levgenid's post “Just above exercise 3 it ...” Just above exercise 3 it states that (2 votes)Want to join the conversation?
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"Where a three-dimensional elastic material obeys Hooke's law,
Energy/volume=(Stress*Strain)/2"
The rubber band we are using for this exercise is a 3-dimensional object and figure 3 is a stress vs strain plot. Notice that the first part of the equation is Energy/volume. When you find the area of the yellow part that corresponds to heat you get an expression of (Energy that is spent on heat)/(Volume of the object). So in order to find the energy spent on heat we have to multiply by the volume.
