Download Ch5. Uniform Circular Motion

Uniform Circular Motion
SP1. Students will analyze the relationships between
force, mass, gravity, and the motion of objects.
g. Measure and calculate centripetal force.
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Uniform Circular Motion
Uniform circular motion is
the motion of an object
traveling at a constant
(uniform) speed on a circular
path.
r
Period (T) is the time required
to travel once around the circle,
that is, to make one complete
revolution.
2r
v
T
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Uniform circular motion emphasizes that
1. The magnitude of the velocity vector, is constant
2. Direction of the vector is not constant
3. Change in direction means there is acceleration
4. Centripetal force causes the acceleration and points
toward the center of the circle
5. Centripetal acceleration points toward the center
of the circle
6. Without the force, there is no acceleration, which
means the object would travel in a straight line
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Centripetal Acceleration
The magnitude of the centripetal acceleration
(ac) depends on the velocity (v) of the object
and the radius (r) of the circular path.
2
v
ac 
r
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A rock tied to a string is traveling at a constant
speed of 4.0 m/s in a circle of radius 1.5 m.
Calculate the magnitude of the centripetal
acceleration of the rock.
Does the size of the rock matter?
How would the acceleration change if…
the rock was spun faster? slower?
the circle was larger? smaller?
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Centripetal Force
The magnitude of the centripetal force (Fc)
depends on the mass (m) and velocity (v) of
the object and the radius (r) of the circular
path.
mv 2
FC 
r
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A 1.5 kg rock tied to a string is traveling at a
constant speed of 2.0 m/s in a circle of radius 3.5 m.
Calculate the magnitude of the centripetal force on
the rock.
What is providing the force?
How would the force change if…
the rock was lighter? heavier?
the rock was spun faster? slower?
the circle was larger? smaller?
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https://www.youtube.com/watch?v=KvCezk9DJfk
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