Saved Bookmarks
| 1. |
A 10 kg ball is dropped from a height of 10m. Find(a) the initial potential energy of the ball , (b) the kinetic energy just before it reaches the ground, and (c) the speed just before it reaches the ground. (Ans: 980J, 980J, 14m/s) |
|
Answer» (a). Mass of the Body = 10 kg. Height = 10 m. Acceleration DUE to gravity = 9.8 m/s². Using the Formula, Potential Energy = mgh = 10 × 9.8 × 10 = 980 J. (B). Now, By the law of the conservation of the Energy, Total amount of the energy of the system remains constant. ∴ Kinetic Energy before the body REACHES the ground is equal to the Potential Energy at the height of 10 m. ∴ Kinetic Energy = 980 J. (c). Kinetic Energy = 980 J. Mass of the ball = 10 kg. ∵ K.E. = 1/2 × mv² ∴ 980 = 1/2 × 10 × v² ∴ v² = 980/5 ⇒ v² = 196 ∴ v = 14 m/s. Hope it helps. |
|