A layer of atmosphere that reflects medium frequency radio waves which is ineffective during night, is

A transverse wave is propagating on the string. The linear density of a vibrating string is $10^{-3} \mathrm{~kg} / \mathrm{m}$. The equation of the wave is $Y=0.05 \sin (x+15 t)$ where $x$ and $Y$ are measured in metre and time in second. The tension force in the string is

The kinetic energy of a revolving satellite (mass $m$ ) at a height equal to thrice the radius of the earth $(R)$ is

A particle executes the simple harmonic motion with an amplitude ' $A$ '. The distance travelled by it in one periodic time is