A rock is tied to the end of a string and whirled around in a circle that describes a vertical plane. The position of the stone when the tension in the string is the greatest is The position of the stone when the tension in the string is the least is 20. 21. For a planet orbiting the Sun, the centripetal force is supplied by 22. If Earth\'s radius and mass were both twice their present values, the acceleration due to gravity at Earth\'s 23. m/s surface would have a value of proportional to the distance the spring moves from equilibrium. The change in momentum of an object is called the A ball is dropped and bounces back to 90% of its original height. The collision between the ball and the law states that the magnitude of the force exerted by an ideal spring is directly 24. 25, ground was The force of attraction between all objects with mass is called total energy is 26. ly moves away from another charge. The force between the two charges changes while the 28. The bending of a wave due to changing speed is called 29. Energy radiates from an atom in bundles called 30. A decay that involves a high speed electron is a(n) 31, The time required to reduce radioactivity by 50% is the decay. Solution 20) The tension in the string is greatest at the bottom of the circle and least at the top. Hence the answer is: bottom , top .