If the initial oscillation of the pendulum has an amplitude of 2.5m , what is the amplitude d of oscillation after 20 s ?

The value is  

Explanation:

From the question we are told that

   The initial amplitude is  A =  2.5 \  m

    The time considered is   t = 20 s

Generally the amplitude at time  t is mathematically represented as

Here is the time constant let assume the value to be

So

=>  

c. rb

explanation:

the atomic radius of a chemical element is a measure of the size of its atoms, usually the mean or typical distance from the center of the nucleus to the boundary of the surrounding shells of electrons.