Question

The bob of a pendulum is released from a horizontal position. If the length of the pendulum is 1.5 m, the speed with which the bob arrives at the lowermost point, given that it dissipated 5% of its initial energy against air resistance?

• A. 3.14 m/s
• B. 6 m/s
• C. 1.54 m/s
• D. 8.26 m/s

Answer 1

The correct option is B 6 m/s

P.E of pendulum is converted in to K.E and lost energy

$P.E=K.E+lostenergy\to 1$

given lost energy =10% of P.E=0.1P.E

P.E=K.E+0.1P.E

0.9P.E=K.E

$0.9mgh=0.5m{v}^2$

$v^2=1.8gh$

h=lenght of the pendulum=2

v = speed at lowest point

g=9.8

now $v=5.94m/s$