Answer:
The surface gravity g of the planet is 1/4 of the surface gravity on earth.
Explanation:
Surface gravity is given by the following formula:

So the gravity of both the earth and the planet is written in terms of their own radius, so we get:


The problem tells us the radius of the planet is twice that of the radius on earth, so:

If we substituted that into the gravity of the planet equation we would end up with the following formula:

Which yields:

So we can now compare the two gravities:

When simplifying the ratio we end up with:

So the gravity acceleration on the surface of the planet is 1/4 of that on the surface of Earth.
Answer:
None
Explanation:
Subatomic particles are the particles which are very smaller than the atoms. Elementary particles are the examples of subatomic particles.
Elementary particles are the particles without any sub-structure which means they are not composed of other particles.
The elementary particles are classified into three categories which are discussed below:
(1) Quarks: up, down, top, bottom, strange, and charm.
(2) Leptons: muon, muon neutrino, electrons, electron neutrino, tau, tau neutrino.
(3) Bosons: Z bosons, W bosons, Higgs, Gluon, photons.
Mesons are the particles which compose one quark and one anti quarks.
Therefore, in the given list there is no meson.