Zero mass force

[sciman55]

Why can't an object with zero mass exert force? What is needed to exert forces (Kinetic energy, Momentum, or something else)? And if a zero mass can't exert force, what would be an alternative physical quanity that can be used to exert force?

 

Do not get me wrong; I know about the speed of light; it has no rest mass but mass by virtue of its motion. Please don't mention light.

[HydrogenBond]

I do not believe that charge has mass but it can exert a force. Although in practical reality, charge does not exist without mass for very long. Charge is far more stable (exists for long periods of time in restricted space) when it is attached to mass, like the electron or proton.

[InfiniteNow]

Why can't an object with zero mass exert force?

Let me question your original premise... why do you believe an object of zero mass cannot exert force?

[sciman55]

Let me question your original premise... why do you believe an object of zero mass cannot exert force?

 

Because I have heard that many times and I know that if zero mass times finite acceleration; it will equal zero force required to move the mass (and/or exert no

force).

 

Why; is something wrong with my original premise?

[Jay-qu]

your reasoning is incorrect. You are talking about conventional mechanical forces. Would you consider an electric field to have mass?

[Tim_Lou]

perhaps you are thinking about the classical F=ma

 

but in reality, the more fundamental equation is:

[math]\vec{F}=\frac{d\vec{p}}{dt}[/math]

 

and the thing is, according to relativity, an object with zero mass can have a non-zero momentum, since:

[math]E^2=(mc^2)+(pc)^2[/math]

if m is zero and E is non-zero, p must be non-zero.

 

hence, the acceleration needs not be "infinite" when a "massless" particle is being "accelerated".

[Qfwfq]

Shine a strong beam of light (oohps!) onto a surface, either opaque or reflecting but not transparent. If the beam is at right angles to a perfectly reflecting mirror, the force will be double than for a matt black surface.