For the situation depicted in Fig., calculate the mechanical energy of the ball. Class 9

For the situation depicted in Fig., calculate the mechanical energy of the ball. Class 9

Question 1.

For the situation depicted in Fig., calculate the mechanical energy of the ball just before it hits the ground and show that even at this position, it is mgh. (Page 129) Class 9

Answer:

Just before hitting the ground (height = 0):

1. Potential energy = mg × 0 = 0.
2. Using v² = u² + 2as = 0 + 2gh → v² - 2gh.
3. Kinetic energy = 1/2 mv² = 1/2 m × 2gh = mgh.
4. Total mechanical energy = KE + PE = mgh + 0 = mgh. This equals the mechanical energy at the top (where KE = 0 and PE = mgh). Hence proved.