Paper 3 · circular motion and projectile motion
A body moves in a circle at constant speed. Which statement correctly explains why it is still accelerating?
AAny object moving along a curved path must be losing speed continuously, which is what defines acceleration.
BAcceleration only occurs when speed changes, so a body moving at constant speed can never be accelerating.
CThe body accelerates only at the instant it starts moving, and travels at constant velocity for the rest of the circular path once it reaches full speed.
DAcceleration is the rate of change of velocity; a constant change of direction changes the velocity even though the speed stays the same.
Explanation: Acceleration is the rate of change of velocity with respect to time. Velocity is a vector, so a continuous change in direction changes the velocity even while the speed (magnitude) stays constant, meaning the body is still accelerating.
Derived from ZIMSEC Physics Paper 3, June 2003, Q1