NCERT Class 9 Science Chapter 7 Work, Energy and Simple Machines Solutions
NCERT Class 9 Science Chapter 7 Work, Energy and Simple Machines Solutions Think It Over (Page No. 116) 1. What will be the magnitude of velocity of the child at the bottom of the blue slide? Answer: Using conservation of mechanical energy (ignoring friction), the potential energy at the top converts entirely to kinetic energy at the bottom: m g h = 1 2 m v 2 v = 2 g h So if the blue slide has height h , the child’s speed at the bottom is √(2gh) . 2. Will two children of different masses reach the bottom of the same slide with the same velocity? Answer: Yes. Notice that mass m cancels out from both sides of the energy equation: m g h = 1 2 m v 2 ⟹ v = 2 g h The final velocity depends only on the height h , not on the mass of the child. So both children reach the bottom with the same speed, regardless of their masses. 3. Which of the slides will result in the largest magnitude of velocity for the child at its bottom? Answer: Again, since v = √(2gh), a greater height h means...