3 ms·

I guess we learned the f=ma format because we had it before calculus? TIL F=dp/dt form... Thanks!

• CamperBob2 2y ago
  Since the photon has nonzero energy E and is moving at c, it has mass by virtue of E=mc^2. And since E=hv, the E part is determined by the photon's frequency v, so the equivalent amount of mass is as well. It shows up as radiation pressure when the photon hits an object, just as if something tangible had collided with it. On a sunny day, I'd guess that sunlight exerts about the same force on an acre on the Earth's surface as a postage stamp lying on the ground.
  • red75prime 2y ago
    E=mc^2 doesn't mean that a photon has mass. Photons do produce gravitational effects due to their energy, but not in the same way as a particle with mass m. See, for example, https://physics.stackexchange.com/a/6222 https://physics.stackexchange.com/a/6222
    • CamperBob2 2y ago
      A photon has no rest mass but it most certainly has mass-energy equivalence.
  • mech422 2y ago
    Thanks for the explanation :-)