HIGHER PHYSICS

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HIGHER PHYSICS

• Upthrust, Floating Sinking

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UPTHRUST
i.e. F pA p ?gh So, Fupthrust ?ghA
Resultant force on object, Fresultant Fweight -
Fupthrust
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Example 1kg iron mass (see Virtual H
Physics) mass, m 1 kg, Fweight mg 1 x 9.8
9.8 N area of base, A 0.0025 m2, depth, h
2 cm 0.02 m Fupthrust ?ghA 1000 x 9.8 x
0.02 x 0.0025 0.49 N Fresultant Fweight
Fupthrust 9.8 0.49 9.31 N
N.B. up thrust increases as depth
increases for fully submerged objects, the
upthrust is constant Fupthrust ?ghA, where
h height of object
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FLOATING SINKING
i.e. Fupthrust Fweight (so, Fresultant 0 N)
If the object gets heavier, it will sink deeper
to increase its upthrust.
If it becomes too heavy, Fupthrust lt F
weight and the object will sink.
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Question