circular motion
TRANSCRIPT
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PhysicsPhysics
Circular Motion
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CircularCircular motionmotion
• Revision
• Circular motion in horizontal
• Vertical circular motion
• Loop-the-loop
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RevisionRevision
• Newton’s Laws
• Circular motion in horizontal circles
• Centripetal force and acceleration
• Angular velocity, frequency & linear velocity
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Newton’s first LawNewton’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.
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No external forceThe body remains at rest.
The body moves with a constant speed.
Newton’s first LawNewton’s first Law
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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.
constant is m if ma F dt
(mv) d F net
Newton’s second LawNewton’s second Law
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For fixed forceA body with a larger mass moves with a smaller acceleration .
A body with a smaller mass moves with a larger acceleration .
Newton’s second LawNewton’s second Law
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For fixed massA 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 LawNewton’s second Law
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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 LawNewton’s third Law
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Body A exerts a force on body B, then body B exerts an equal and opposite force on body A.
Newton’s third LawNewton’s third Law
Body A Body B
Force on B by AForce on A by B
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Newton’s third LawNewton’s third Law
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Circular Motion in horizontal circlesCircular Motion in horizontal circles
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Circular Motion in horizontal circlesCircular Motion in horizontal circles
Angular velocity = / t
Linear velocity v = r Centripetal force
F = m r 2 = m v2 / r
Centripetal accelerationa = r 2 = v2 / r
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Circular Motion in horizontal circlesCircular Motion in horizontal circlesConical pendulumConical pendulum
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Circular Motion in horizontal circlesCircular Motion in horizontal circlesConical pendulumConical pendulum
Do you remember what kind of forces provides the centripetal force to the bob ?
Tension T
Weight mg
Centripetal force
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Vertical circular motion Vertical circular motion Bucket and waterBucket and water
Does the water spill out the bucket when whirling ?
If no, why doesn’t it spill out ?
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Vertical circular motion Vertical circular motion Bucket and waterBucket and water
What kind of motion does thebucket perform ?
Vertical circular motion
What kind of force provides the centripetal force Fc to thebucket ?
Tension T
Weight mg
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Vertical circular motion Vertical circular motion Bucket and waterBucket and water
What kind of force providesthe centripetal force Fc to the bucket at the highest position ?
Fc = T + mg
Tension T Weight mg
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Vertical circular motion Vertical circular motion Bucket and waterBucket and water
What kind of force providesthe centripetal force Fc to the bucket at the lowest position ?
Fc = T - mgTension T Weight
mg
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Vertical circular motion Vertical circular motion Bucket and waterBucket and water
What kind of force provides the centripetal force Fc to the water at the highest position ?
Fc = R + W Reaction of the bucket
R
Weight of water
W
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Vertical circular motion Vertical circular motion Bucket and waterBucket and water
What kind of force providesthe centripetal force Fc to the bucket at the lowest position ?
Fc = R - W
Reaction of the bucket
R
Weight of water
W
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Vertical circular motion Vertical circular motion Loop-the-loopLoop-the-loop
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Vertical circular motion Vertical circular motion Loop-the-loopLoop-the-loop
What kind of force providesthe centripetal force Fc to the mass ?
The reaction of the track
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M.C. Exercise
Class Class exercisesexercises
Mainmenu
True or False
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M.C. Question 1
Which of the following formula
shows Newton’s second Law ?
v = r = / tF = maa = v2 / r
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M.C. Question 2
At which position is the tension
on the bucket largest ?
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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.
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True False
In the Ocean Park , cart coast rider
can loop the loop by tension.
True or False Question 2