# Solenoid Kinetic Energy

I found this solenoid on Sparkfun (https://www.sparkfun.com/datasheets/Robotics/ZHO-1364S-36A13.pdf) and according to the datasheet it is able to provide a force between 36N and 5N depending on the current travel position (see page 3). I approximated this in an excel sheet, calculating the accelleration of a mass that is being pushed by the soleniod: $$a=F/m$$ $$v^2=2*a*s$$ $$E_{kin}=1/2*m*v^2$$ Somehow, these values seem to be way too high when compared to an traditional, spring-loaded system where I would get around 3 Joule out of an 200N spring. Is there an mistake in my calculation? I have a feeling that it might have something to do with the speed the solenoid itself is moving.

• Your graph shows force max at a little over "30" and force min at a little below "5". This seems to tally with the data sheet so, what is the issue here? – Andy aka Jul 27 '17 at 11:51
• @Andyaka The problem is that the energy is unbelievably high. – mxcd Jul 27 '17 at 12:06
• I suppose you either believe the data sheet or you don't. Perhaps you'd have more confidence if you bought from a mechanical supplier, and had broad tables to select from, – Scott Seidman Jul 27 '17 at 12:20
• Your second equation looks wrong. Do your dimensional analysis to convince yourself the units on both sides don't match up. This isn't electrical engineering BTW – Scott Seidman Jul 27 '17 at 12:35
• Why don't you just use the area under the force-distance graph to compute the kinetic energy directly? – Jon Jul 27 '17 at 13:21

## 1 Answer

The datasheet for the solenoid is showing the attracting force for a mass attached to the plunger when the solenoid is oriented in the vertical direction and the mass hangs from the plunger. This is simply showing the maximum mass for which the solenoid can minimally counter the acceleration of gravity.

Given the shape of the graph, it suggests that at the specified mass there is zero movement of the plunger from its plotted position. It follows then that the acceleration and velocity of the plunger, and therefore the mass, is likely zero throughout the plot.