Circular Motion Section 7 1 Objectives By the

Circular Motion Section 7. 1

Objectives: By the end of class you should be able to… • Define tangential speed. • Calculate centripetal acceleration. • Calculate centripetal force.

When the tangential speed is constant, the motion is described as uniform circular motion.

Tangential speed depends on the distance from the object to the center of the circular path.

Centripetal means center seeking. Centripetal acceleration is the acceleration directed toward the center of a circular path. Centripetal acceleration is ALWAYS directed toward the center of a circle.

A rope attaches a tire to an overhanging tree limb. A girl swinging on the tire has a centripetal acceleration of 3. 0 m/s 2. If the length of the rope is 2. 1 m, what is the girl’s tangential speed?

Tangential acceleration is due to a change in speed. This does not occur in uniform circular motion.

When an object is in circular motion, it experiences centripetal acceleration directed toward the center of motion. The net force directed toward the center of the circular path is called centripetal force.

Centripetal force is simply the name given to the net force toward the center of the circular path followed by an object moving in uniform circular motion. Any type of force or combination of forces can provide this net force. For example, friction between a racecar’s tires and a circular track is a centripetal force that keeps the car in a circular path. As another example, gravitational force is a centripetal force that keeps the moon in its orbit.

A pilot is flying a small plane at 56. 6 m/s in a circular path with a radius of 188. 5 m. The centripetal force needed to maintain the plane’s circular motion is 1. 89 × 104 N. What is the plane’s mass?

A 2. 10 m rope attaches a tire to an overhanging tree limb. A girl swinging on the tire has a tangential speed of 2. 50 m/s. If the magnitude of the centripetal force is 88. 0 N, what is the girl’s mass?

Centripetal force is NECESSARY for circular motion. Because centripetal force acts at right angles to an object’s circular motion, the force changes the direction of the object’s velocity. If this force vanishes, the object stops moving in a circular path. Instead, the object moves along a straight path that is tangent to the circle. Inertia is often misinterpreted as a force.