motion in a straight line at constant speed is called rotational speed.
motion in a straight line at constant speed is called?
rotational speed
the constancy of areal velocity may be illustrated by uniform circular and linear motion. in uniform circular motion, the particle moves with constant speed "v" around the circumference of a circle of radius "r". since the angular velocity ω = "v"/"r" is constant, the area swept out in a time δ"t" equals ω "r"δ"t"; hence, equal areas are swept out in equal times δ"t". in uniform linear motion (i.e., motion in the absence of a force, by newton's first law of motion), the particle moves with constant velocity, that is, with constant speed "v" along a line. in a time δ"t", the particle sweeps out an area ½"v"δ"tr" (the impact parameter). the distance "r" does not change as the particle moves along the line; it represents the distance of closest approach of the line to the center o (the impact parameter). since the speed "v" is likewise unchanging, the areal velocity ½"vr" is a constant of motion; the particle sweeps out equal areas in equal times.
classical central-force problem
to have a constant velocity, an object must have a constant speed in a constant direction. constant direction constrains the object to motion in a straight path thus, a constant velocity means motion in a straight line at a constant speed.





















































for example, a car moving at a constant 20 kilometres per hour in a circular path has a constant speed, but does not have a constant velocity because its direction changes. hence, the car is considered to be undergoing an acceleration.





















































section::::difference between speed and velocity.
velocity