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Let \(a_r\) and \(a_t\) represent radial and tangential acceleration. The motion of a particle may be circular if

1. \(a_r=0,\ a_t=0\)
2. \(a_r=0,\ a_t\neq 0\)
3. \(a_r\neq 0,\ a_t=0\)
4. none of these

Correct answer: \(a_r\neq 0,\ a_t=0\)

Solution

For a particle to move in a circle, there must be a radial (centripetal) acceleration directed toward the center. If tangential acceleration is zero, the speed remains constant, giving uniform circular motion. Thus the motion may be circular when \(a_r\neq 0\) and \(a_t=0\).

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