We divide the thin rectangular sheet in small parts of height b and length dr. All these sheets are parallel to b. The infinitesimal moment of inertia of one of these small parts is

where

Now we find the moment of inertia by integrating from

to

The moment of inertia is

(from (-a/2) to

(a/2))
Crates is the correct answer because they create dents that make the bumps of mountains.
Answer:
the Restoring force causes the vibrating object to go slower going further from the equilibrium position and to go faster as it approaches the equilibrium position. the restoring force is what is causing the vibration The tension force comes from the string tugging on the bob of the pendulum.
Explanation: