17 Joules of Energy From a Mouse Trap Do you think it would be possible to get 17 joules out of a standard size mouse trap. By my math, it is a torsion coefficient of 3.45 or so out of the spring.
 A: I haven't used a mousetrap for several decades, but as I recall the moving arm is about 5cm long, so the tip moves 0.05$\pi$ or about 0.16m. To get 17J of work the force at the tip of the arm would need to be 100N. I'm fairly sure the force isn't anything like that great. I remember being able to pull the arm back with one finger. I would guess the force is nearer 10N, so you'd only get around 2J out.
A: Good guesstimating John Rennie.  This fellow did some measurements (on a rat trap) and got slightly over 3 Joules:
http://www.instructables.com/id/Mouse-Trap-Speed/step4/Analysis-using-Basic-Physics/
A: Yes, if you burn it. Neglecting the metal, a $25\ g$ wooden mousetrap at $15\ MJ/kg$ should yield about $375\ kJ$. 
A: $$U=\frac{1}{2}k\theta^2$$.
A standard mouse trap is usually set at $\approx 180^o=\pi\space$ radians. $$\therefore U=0.5*3.45*\pi^2\approx17.025\space J$$
Of course, the torsion law is only an approximation, and it may decrease after use of the moustrap, so the energy obtained would be slightly less.
EDIT:
I seem to have misunderstood your question.
I don't have any idea what the torsion constant of a spring should be, but 17 joules is pretty small.
A: Took the following data:
measured force on 0.045 m trap arm and computed torque
(angle(rad),  torque(n*m))
(0 ,        .1215)
   (1.57 ,     .2565)
   (3.14 ,     .378)
best fit line to data  torque = .0816 * angle + 0.1238
area under this line is energy stored in spring
about 0.8 Joules
A: I clamped a small mousetrap to a heavy table and used a spring scale to measure the force when the hook was attached to the trap arm. Try to keep a 90 degree angle between the scale line of action and the arm of the mousetrap. The trap arm I measured was about 45 mm in length from the pivot point.  I measured three forces, one to just lift the trap arm off the wooden base, a second when the arm has rotated 90 degrees (pi/2 rad) and a third when the trap are was almost in contact with the wood and having been rotated 180 degrees (pi rad).  I had to trim some wood away for the last reading and clamp the trap overhanging the table.  The force is multiplied times the lever arm of 45 mm to find the torque as a function of the angle of rotation.  It is pretty much a straight line which is good since we would expect some sort of Hooke's law relationship.  It can be shown that an increment of work is the torque times an increment of the angle of rotation.  Thus integration of the torque function over the change in angle (area under torque-angle function) is the total work that can be done by the mousetrap when released to stop.  I have repeated this experiment a few times and the work of the trap comes out to be between 0.7 and 0.8 joules.
A: TL;DR: No, 3.45 as a torsional constant is almost 40 times that of a regular mousetrap.
I calculated the torsion constant in a Victor Original Mousetrap (EDIT: with spring arm length of 4.3cm) to be approximately $0.09088 [\frac{N*m}{Rad}]$ by using Hooke's Law and comparing the angle between the spring arm and the wood base when hanging different weights from the arm with the trap upside down.
I then used $τ=-kθ$ (torque applied to the spring arm by the weight is equal to torsional constant times the angle rotated) along with the values from one of the weights to calculate how far the spring is twisted by default ($θ = \frac{τ_{weight}}{k} - θ_{weight}$). This came out to about 73.63°.
I used this 'starting angle' to calculate how much potential energy ($U = \frac{1}{2}kθ^2$) the spring would have when totally open (an additional 180° from that last angle we found). The MAXIMUM energy that you could get out of this "standard" mousetrap is approximately 0.815 [J]. Over 20 times less than what you need.
If anyone wants more information I'm happy to post a link to my work.
A: I tried duplicating the author's experiment to measure the spring constant and energy of the Victor original mousetrap.  I actually measured a spring constant of 0.976 Newton-meters per radian and an energy content of 9 Joules for 180 degrees (i.e., from totally open to totally tripped.)  I did find nearly the same original twist of -78 degrees.  The author possibly forgot the acceleration of gravity (9.8 m/s^2) when computing the downward force in Newtons from a mass of kilograms since my numbers are a factor of about 10 times higher.
