The characteristic distance at which quantum gravitational effects are significant, the Planck length, can be determined from a suitable combination of the fundamental physical constants G, h and c.

Which of the following correctly gives the Planck length ?

A body of mass 2 kg slides down with an acceleration of 3 m/s² on a rough inclined plane having a slope of $${30^o}$$. The external force required to take the same body up the plane with the same acceleration will be : (g = 10 m/s²)

A constant voltages is applied between two ends of a metallic wire. If the length is halved and the radius of the wire is doubled, the rate of heat developed in the wire will be :

Muon ($$\mu $$^$$-$$) is a negatively charged (|q| = |e|) particle with a mass m_{$$\mu $$} = 200 m_e, where m_e is the mass of the electron and e is the electronic charge. If $$\mu $$^$$-$$ is bond to a proton to form a hydrogen like atom, identify the correct statements.
(A)   Radis of the muonic orbit is 200 times smaller than that of the electron.
(B)   The speed of the $$\mu $$^$$-$$ in the n^th orbit is $${1 \over {200}}$$ times that of the electron in the n^th orbit.
(C)   The ionization energy of muonic atom is 200 timesmore than of an hydroen atom.
(D)   The momentum of the muon in the n^th orbit is 200 times more than that of the electron.