AL Physics Circular Motion

Circular motion Revision Circular motion in horizontal Vertical circular motion Loop-the-loop

Revision Newton’s Laws Circular motion in horizontal circles Centripetal force and acceleration Angular velocity, frequency & linear velocity

Newton’s first Law A body continues in a state of rest or uniform motion in a straight line unless it is acted upon by external forces.

No external force The body remains at rest. The body moves with a constant speed. Newton’s first Law

The rate of change of momentum of a body is proportional to and in the same direction as the resultant force that acts on it. Newton’s second Law

For fixed force A body with a larger mass moves with a smaller acceleration. A body with a smaller mass moves with a larger acceleration. Newton’s second Law

For fixed mass A body with a smaller net force moves with a smaller acceleration. A body with a larger net force moves with a larger acceleration. Newton’s second Law

If one body exerts a force on another, there is an equal and opposite force, called reaction, exerted on the first body. Newton’s third Law

Body A exerts a force on body B, then body B exerts an equal and opposite force on body A. Newton’s third Law Body A Body B Force on B by AForce on A by B

Newton’s third Law

Circular Motion in horizontal circles

Angular velocity  =  / t Linear velocity v =  r Centripetal force F = m r  2 = m v 2 / r Centripetal acceleration a = r  2 = v 2 / r

Circular Motion in horizontal circles Conical pendulum

Do you remember what kind of forces provides the centripetal force to the bob ? Tension T Weight mg Centripetal force

Vertical circular motion Bucket and water Does the water spill out the bucket when whirling ? If no, why doesn’t it spill out ?

Vertical circular motion Bucket and water What kind of motion does the bucket perform ? Vertical circular motion What kind of force provides the centripetal force F c to the bucket ? Tension T Weight mg

Vertical circular motion Bucket and water What kind of force provides the centripetal force F c to the bucket at the highest position ? F c = T + mg Tension T Weight mg

Vertical circular motion Bucket and water What kind of force provides the centripetal force F c to the bucket at the lowest position ? F c = T - mg Tension TWeight mg

Vertical circular motion Bucket and water What kind of force provides the centripetal force F c to the water at the highest position ? F c = R + W Reaction of the bucket R Weight of water W

Vertical circular motion Bucket and water What kind of force provides the centripetal force F c to the bucket at the lowest position ? F c = R - W Reaction of the bucket R Weight of water W

Vertical circular motion Loop-the-loop

What kind of force provides the centripetal force F c to the mass ? The reaction of the track

M.C. Exercise Class exercises Main menu True or False

M.C. Question 1 Which of the following formula shows Newton’s second Law ? v = r   =  / t F = ma a = v 2 / r

M.C. Question 2 At which position is the tension on the bucket largest ?

True or False Question 1 True False If the angular velocity of the bucket at the top position is too small, water may spill out.

TrueFalse In the Ocean Park, cart coast rider can loop the loop by tension. True or False Question 2

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