Question

The string of a pendulum 2m long . The bob is pulled sideways so that the string becomes horizontal when the bob is released . What s the speed when the bob reaches the lowest point. Assume that 10 % of its energy is used for air resistence

Answer 1

the sum of 2+10 is = 12 is the answer

Answer 2

Answer:

Explanation:

At point A total energy = mgl

Now 10 percent energy is used. So, remaining energy=9/10*mgl

At lowest point B, l=0

So total energy at B =1/2m*v*v

Using law of conservation of energy.

1/2m*v*v=9/10mgl

1/2*v*v=9/10gl

1/2*v*v=9/10*10*2

v*v=36

v=6m/sec