## How to change speed into force

Perhaps a more direct concept of changing speed into force is the idea of electromagnetic induction, the principle operating within an electric motor. The motion (speed?) of an electric charge creates a magnetic field, which in turn applies a force to a magnet.

In the mechanical world in general, speed (velocity, really) and force directly imply each other. Intuitively we know how force changes into speed: the classic equation F=ma (force equals mass times acceleration). Intuitively, this means that a force, applied to an object with mass, will accelerate that mass, i.e., change its velocity. So we say that the force causes the acceleration: force becomes speed.

But this causation is not actually in the equation ... indeed, this equation is reversible like most physics relationships. So we can also interpret it as follows: any change in velocity (an acceleration) implies that there must have been a force.

Can we conclude, therefore, that the change in velocity caused the force? That speed "changed into" force? For electromagnetism, that's a reasonable interpretation. For electrostatic forces (like those car crashes in other answers), probably not.

I suppose one could say that the kinetic energy (speed) of the quarks in protons and neutrons deform spacetime, "changing" into gravitational force, but that feels like a stretch (as does relativistic frame dragging).

You can put the thing that has some speed in a viscous fluid (damper). Multiplication is force. Of course you will dissipate energy but feel force
###### How are scientists at CERN able to get subatomic particles in the LHC?

Briefly, with electromagnetic fields. We only collide electromagnetically charged particles, because we can't control the other fundamental forces like we can the EM ones.In practice this means that we ionise hydrogen (and sometimes lead and gold) to get charged protons and ions, then use a series of radio-frequency electric and magnetic fields

###### Do people in Roswell, NM actually believe the alien theory?

To be honest, most people who live in Roswell don't think about the alien thing all that much. When the topic does come up, there is the same range of reactions as you would get anywhere. There are some locals

###### What is the scientific approach that makes economics a science?

This is a topic on which there isn't a strong consensus. The majority of what you might call ‘mainstream' economists approach economics like one of the hard sciences, like physics or chemistry. Some other schools of economic thought - notably the Austrian economists - believe that economics is an a priori science, like geometry. The difference? The former