We call the acceleration of an object moving in uniform circular motion the centripetal acceleration a c because centripetal means center seeking. If we imagine Δ s Δ s becoming smaller and smaller, then the acceleration would point exactly toward the center of rotation, but this case is hard to draw. (The center of rotation is at the center of the circular path).
Acceleration is in the direction of the change in velocity in this case it points roughly toward the center of rotation. The direction of the instantaneous tangential velocity is shown at two points along the path. Ask students what would happen if you suddenly cut the string? In which direction would the object travel? Why? What does this say about the direction of acceleration? Ask students to give examples of when they have come across centripetal acceleration.įigure 6.7 shows an object moving in a circular path at constant speed. Demonstrate circular motion by tying a weight to a string and twirling it around. The sharper the curve and the greater your speed, the more noticeable this effect becomes. This fictitious force is known as the centrifugal force. Inside the car it appears as if you are forced away from the center of the turn. This isn’t an actual force that is acting on you-it only happens because your body wants to continue moving in a straight line (as per Newton’s first law) whereas the car is turning off this straight-line path. What you notice is a feeling of sliding (or being flung, depending on the speed) away from the center of the turn. If you hold the steering wheel steady during the turn and move at a constant speed, you are executing uniform circular motion. You experience this acceleration yourself every time you ride in a car while it turns a corner. Therefore, an object undergoing uniform circular motion is always accelerating, even though the magnitude of its velocity is constant. We know from kinematics that acceleration is a change in velocity, either in magnitude or in direction or both. Note that, unlike speed, the linear velocity of an object in circular motion is constantly changing because it is always changing direction. The simplest case of circular motion is uniform circular motion, where an object travels a circular path at a constant speed. In the previous section, we defined circular motion. Ask students to give examples of circular motion.
Circular motion manual#
In addition, the High School Physics Laboratory Manual addresses content in this section in the lab titled: Circular and Rotational Motion, as well as the following standards:
However, in two- and three-dimensional kinematics, even if the speed is a constant, a particle can have acceleration if it moves along a curved trajectory such as a circle.
In one-dimensional kinematics, objects with a constant speed have zero acceleration.
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