Physics 621A
–
Extra Practice
Sections 11.2, 12.1
1.
A runner moving at a speed of 8.8 m/s rounds a bend in the track with a
radius of curvature of 25 m.
a.
Calculate the centripetal acceleration of the runner.
3.1 𝑚/?
2
b.
What force supplies the centripetal force to give this acceleration to
the runner?
friction
2.
A 40.0 g stone is whirled in a horizontal circle on the end of a 60.0 cm string
at a speed of 2.2 m/s. Calculate the tension in the string.
0.32 N
3.
A yo-yo with a mass of 255 g is twirled at a constant speed of 2.5 m/s in a
vertical circle on a string with a length of 34.5 cm
a.
Calculate the tension in the string at the top of the revolution.
2.1 N
b.
Calculate the tension in the string at the bottom of the revolution.
7.1 N
c.
Calculate the maximum speed the yo-yo can have if the string will
break when the tension reaches 22.4 N.
5.2 m/s
4.
The Moon orbits the Earth with a period of approximately 27.3 days. If the
distance from Earth to the Moon is
3.8 × 10
5
m,
a.
Calculate the magnitude of the Moon
’
s centripetal acceleration.

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