Work Energy and Power

Given Data
Length of pendulum, l=200cm=2m
Released from horizontal position ⟶ Initial height (relative to mean position) l=2m
Acceleration due to gravity, g=10m∕s2
10% of energy lost due to air resistance
Step 1: Initial Potential Energy
At horizontal position (bob just released):
E‌initial ‌=mgh=mgl=m(10)(2)=20mJ
Step 2: Energy Lost in Air Resistance
10% of energy is lost ⟶ only 90% remains.
E‌mean ‌=0.9×E‌initial ‌=0.9×20m=18mJ
Step 3: Energy at Mean Position
At mean position, the bob has only kinetic energy (potential energy =0 :
‌

1

2

mv2=18m
v2=36⇒v=6m∕s
Final Answer:
v=6m∕s