The mean radius of the earth's orbit round the sun is $1.5 \times 10^{11}.$ The mean radius of the orbit of mercury round the sun is $6 \times10^{10}\,m.$ The mercury will rotate around the sun in
A year
Nearly $4$ years
Nearly $\frac{1}{4}$ year
$2.5$ years
A satellite $A$ of mass $m$ is at a distance of $r$ from the centre of the earth. Another satellite $B$ of mass $2m$ is at a distance of $2r$ from the earth's centre. Their time periods are in the ratio of
A satellite is in a circular equatorial orbit of radius $7000\,km$ around the Earth. If it is transferred to a circular orbit of double the radius then its angular momentum will be
The planet Mars has two moons, phobos and delmos.
$(i)$ phobos has a period $7$ hours, $39$ minutes and an orbital radius of $9.4 \times 10^{3} \;km .$ Calculate the mass of mars.
$(ii)$ Assume that earth and mars move in circular orbits around the sun. with the martian orbit being $1.52$ times the orbital radius of the earth. What is the length of the martian year in days?
The time period of a geostationary satellite is $24\; \mathrm{h}$, at a helght $6 \mathrm{R}_{\mathrm{E}}( \mathrm{R}_{\mathrm{E}}$ is radius of earth) from surface of earth. The time period of another satellite whose helght is $2.5 \mathrm{R}_{\mathrm{E}}$ from surface will be
The ratio of the distances of two planets from the sun is $1.38$. The ratio of their period of revolution around the sun is