The automobile beltway around many cities is approximately circular. suppose that you start driving at point a on the east side of the beltway and drive counterclockwise at an unchanging 90 km/hr (figure 3.13). as you pass point b on the north side, what is your speed? your velocity?

speed is the magnitude of velocity which is given as 90 km/hr and it does not change. only the direction change , the direction at any time is given by the tangent to the circle at that time and location.

from the diagram , at north side, the velocity is directed in west direction

luster is not a good characteristic to use by itself because luster is the property of minerals that indicates how much the surface of a mineral reflects light. the luster of a mineral is affected by the brilliance of the light used to observe the mineral surface.