The nitrogen molecules in Exercise 19.1 move considerably faster than the pendulum and continuously bombard the pendulum from all sides.

(a) Why does this bombardment slow the pendulum down? 

(b) When the pendulum is at rest, why don't we see the effects of this continuous bombardment?

Data from Exercise 19.1

Consider a \(0.10-\mathrm{kg}\) pendulum swinging at a maximum speed of \(0.80 \mathrm{~m} / \mathrm{s}\) inside a box that contains \(1.0 \times 10^{23}\) nitrogen molecules. The mass of a nitrogen molecule is \(4.7 \times 10^{-26} \mathrm{~kg}\), and at room temperature a typical nitrogen molecule moves at \(500 \mathrm{~m} / \mathrm{s}\). What are 

The mechanical energy of the pendulum, 

The average kinetic energy of one nitrogen molecule, and

The sum of the average kinetic energies of all the nitrogen molecules?