Question

The string of a pendulum is `2.0m` long. The bob is pulled sideways so that the string becomes horizontal and then the bob is released. What is the speed with which the bob arrives at the lowest point ? Assume theat `10%` of initial energy is dissipated against air resistance. Take `g=10m//s^(2)`

Answer 1

Here, `l=2.0m, ` when the string becomes horizontal,
`h=l=2.0m`
Let `upsilon` be the speed with which the bob arrives at the lowest point. As `10%` of energy is dissipated, therefore
`(1)/(2)m upsilon^(2)=(90)/(100)(mgh)`
`upsilon=sqrt(2xx(9)/(10)gh)`
`upsilon=sqrt((2xx9xx10xx2.0)/(10))=6.0m//s`