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Zynoakib
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Homework Statement
A small container of water is placed on a turntable
inside a microwave oven, at a radius of 12.0 cm from
the center. The turntable rotates steadily, turning one
revolution in each 7.25 s. What angle does the water
surface make with the horizontal?
Homework Equations
F = ma
a = v^2/ r
The Attempt at a Solution
Find the velocity of rotation:
0.12 x 2 x pi/ 7.25= 0.1 m/s
Find the centripetal acceleration:
(0.1)^2/ 0.12 = 0.09 ms^-2
Centripetal acceleration = 0.09 ms^-2 = horizontal acceleration
Gravitational acceleration = 9.8 ms^-2 = vertical acceleration
Angle make wit the horizontal surface
arctan (9.8/0.09) = 89 degree
I know it should have been arctan (0.09/9.8) = 0.526 degree (the actual answer), but in this way the centripetal acceleration would become the vertical acceleration whereas the gravitational acceleration would become horizontal acceleration.
What's wrong?
Thanks!
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