Rotating Frames of Reference

Going Around a Corner What happens when you drive around in a corner in a car? Are you in an inertial or non-inertial frame of reference?

Centrifugal Force Centri – Centre, Fugal – Fleeing Fictitious force A centre fleeing force Fictitious force Directed outwards from the centre of the circle Only exists in a non-inertial frame of reference

Gravitron In the Gravitron, you feel a force pushing you into the wall. This is a non-inertial frame of reference. Newton’s 1st says you should fly (on a tangent) out of the rotating device Centripetal force is accelerating you towards the centre. In the non-inertial frame of reference (rotating frame) we use a centrifugal force to explain why you are pressed into the wall

The Centrifuge

Physics Funnies!!!

Physics Funnies!!!

Physics Funnies!!!

A NEW Coordinate System!!! Have the x axis always follow the centripetal acceleration of the system In all uniform circular motion this is along the horizontal diameter of the circle so that it moves through the middle of the object + X axis

Centripetal Force Start with Newton’s second law! Include centripetal acceleration… This net force is now called the centripetal force. A centripetal force maintains centripetal acceleration!

Analyzing Forces in uniform circular motion

What is the centripetal force?

What is the centripetal force?

What is the centripetal force?

What is the centripetal force?

What is the centripetal force?

Example 1 A car is travelling around a corner at 80km/hr. The radius of the curve is 0.40km. What is the coefficient of friction on the ground?

Example 2 What is the force of gravity acting on the Earth from the Sun? Use uniform circular motion calculations. What do we need to know? Double check with Fg=Gm1m2/r2

Example 3 A ball is attached to the end of a string. The ball is spun in a circle on a vertical plane at a constant speed. Calculate the force of tension at the top of the loop.

Example 4 A ball is attached to the end of a string. The ball is spun in a circle on a vertical plane at a constant speed. Calculate the force of tension at the bottom of the loop.

Example 5 A ball is attached to the end of a string. The ball is spun in a circle on a horizontal plane at a constant speed. Calculate the force of tension at a position in the loop.

Example 6 A car moves around a 0.40km banked curve with UCM at 80km/hr. Assuming the curve is frictionless, what is the angle of the bank?

Analyzing Forces in UCM Take a look at the flying pig Determine at what angle the string is at.

Path of Spacecraft to Mars

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