Identify two types of motion where an object's speed remains the same while it continues to change direction

Explanation:

1) Any motion in which the acceleration is orthogonal to the direction of travel will have this characteristic:

  circular motion in a plane

  motion of a charged particle in a magnetic field perpendicular to the direction of travel

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2) Motion in which the speed is constant, regardless:

  motion of a photon through a varying gravitational field

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.