Given Data
Length of pendulum,
l=200cm=2mReleased from horizontal position
⟶ Initial height (relative to mean position)
l=2mAcceleration due to gravity,
g=10m∕s210% of energy lost due to air resistance
Step 1: Initial Potential Energy
At horizontal position (bob just released):
E‌initial ‌=mgh=mgl=m(10)(2)=20mJStep 2: Energy Lost in Air Resistance
10% of energy is lost
⟶ only
90% remains.
E‌mean ‌=0.9×E‌initial ‌=0.9×20m=18mJStep 3: Energy at Mean Position
At mean position, the bob has only kinetic energy (potential energy
=0 :
‌mv2=18m v2=36⇒v=6m∕sFinal Answer:
v=6m∕s
