A body moving in a circle at constant speed
Correct answer: B. is accelerating, because the direction of its velocity is continuously changing
- A. has zero acceleration
- B. is accelerating, because the direction of its velocity is continuously changing
- C. has a constant velocity
- D. experiences no net force
Explanation
Velocity is a vector, so changing its direction is a change in velocity even when the magnitude is fixed, and that change per unit time is the centripetal acceleration directed towards the centre. A net force must therefore act, supplied by tension, gravity, friction or the normal force depending on the situation. This is the single most tested idea in circular motion.
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About Angular Velocity
Angular velocity describes how quickly angular displacement changes with time, with ω = Δθ/Δt and units of radians per second. Questions relate angular and linear motion through v = rω, use the direction given by the right hand rule, and distinguish angular velocity from angular acceleration and ordinary frequency.
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