An object of mass m is traveling on a horizontal surface. there is a coefficient of kinetic friction μ between the object and the surface. the object has speed v when it reaches x=0 and encounters a spring. the object compresses the spring, stops, and then recoils and travels in the opposite direction. when the object reaches x=0 on its return trip, it stops.

half of a circle

explanation:

the arrow and the top of the circle is matching together. it is not a polygon because a polygon would always be the same shape. therefore, an half of a circle is called semicircle so you would find the radius of it.

the part of the wave he is travelling on is the crest

the motion of a pendulum is a classic example of mechanical energy conservation. a pendulum consists of a mass (known as a bob ) attached by a string to a pivot point. as the pendulum moves it sweeps out a circular arc, moving back and forth in a periodic fashion.