The gravitational potential difference between the surface of a planet and a point $20\ m$ above it is $16\ J/kg$. Then calculate the work done in moving a $4\ kg$ mass by $8\ m$ on a slope $60$ degree from the horizontal, is:

At what height from the ground will be the value of $g$ be the same as

that in $10 km$ deep mine below the surface of earth.

Gravity meters measures in units of mGal where 1 Gal (or 1 galileo) is the C.G.S unit of acceleration due to gravity. A gravity meter shows a reading of +300 mGal at a place where the normal 'g' is 9.78 $m s^{-2}$. The correct 'g' at that place where the reading was taken is _____ $m s^{-2}$.

বিষুবীয় অঞ্চল থেকে মেরু অঞ্চলের দিকে অভিকর্ষীয় ত্বরণ- 

চিত্রে মসৃণ আনত তল বেয়ে গড়িয়ে পড়া বস্তুর ত্বরণ-