Answer:
- motion in which acceleration is orthogonal to travel direction
- motion in which speed is constant
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
