The method of soil conservation in which stones, grass, soil are used to build barriers along contours and trenches are made in front of the barriers to collect water is called?
If the acceleration due to gravity on the surface of earth is g, then the acceleration due to gravity on the surface of a planet whose mass is same as that of earth and radius is twice as that of earth is _________________.
A Sonar of a ship sends sounds waves of speed 1500 m/s. These waves are reflected back by the ocean floor in 5 seconds. Find the depth (in m) of the ocean floor.