Example 11.8 - Chapter 11 Class 9 - Work and Energy
Last updated at April 16, 2024 by Teachoo
Examples from NCERT Book
Last updated at April 16, 2024 by Teachoo
Example 11.8 A boy of mass 50 kg runs up a staircase of 45 steps in 9 s. If the height of each step is 15 cm, find his power. Take g = 10 m sā2.Mass of body = m = 50 kg Time taken = t = 9 s Height of 1 step = 15 cm = 15/100 m = 0.15 m Total Height Climbed = Height of 45 steps h = 45 Ć 0.15 h = 6.75 m Acceleration due to gravity = g = 10 m/s2 Power = (šššš šššš)/(šššš š”šššš) Work done = Potential energy of body = m Ć g Ć h ā“ Power = (š Ć š Ć ā)/š” = (50 Ć 10 Ć 6.75)/9 = (500 Ć 675)/(9 Ć 100) = (5 Ć 675)/9 = 5 Ć 75 = 375 W