# circular motion

Circular Motion – movement with constant speed around in a circle: a circular path or a circular orbit. It is one of the simplest cases of accelerated motion. Circular motion involves acceleration of the moving object by a centripetal force which pulls the moving object towards the center of the circular orbit. Without this acceleration, the object would move inertially in a straight line, according to Newton’s first law of motion. Circular motion is accelerated even though the speed is constant, because the velocity of the moving object is constantly changing.

Examples of circular motion are: an artificial satellite orbiting the Earth in geosynchronous orbit, a stone which is tied to a rope and is being swung in circles (cf. hammer throw), a racecar turning through a curve in a racetrack, an electron moving perpendicular to a uniform magnetic field, a gear turning inside a mechanism.

Satellite Motion

That’s engineering

• acceleration – the rate of change of velocity. length/time² or metre/second². To accelerate an object is to increase its velocity over a period of time.
• centripetal force – the force pulling an object toward the center of a circular path as the object goes around the circle. An object can travel in a circle only if there is a centripetal force on it. For an object at the end of a rope, the centripetal force is the tension of the rope and acts towards whatever the rope is anchored to.

Engineering ideas

• centrifugal force, centripetal force, acceleration, speed, velocity, curved path, linear, vertical, horizontal, balance, weight, mass, bank, incline, weightlessness, parabolic

Do It
Challenges for you to work on…

• Anti-gravity Marble – Make the marble stay in the can while having it turned upside down and off the surface of the table.