Page 115 - Physics

Sinking and fl oating

(a)
(a) (b)
(b)
Empty pty
beaker
beaker
Digital balance
Digital balance
Spring balance
Spring balance

(c) Beakerer
(c)
with water
with water
Piece of wood Digital balance
Digital balance

Figure 5.8
3. Fill the transparent beaker with water to about 3/4 of its height and weight it as
shown in Figure 5.8 (c).
4. Place the wood on the surface of the water and record its apparent weight.
5. Measure and record the water level when the wood is placed on the surface of the water.
6. Place a small weight on the fl oating wood.
7. Measure the water level and the depth of submersion of the wood after adding
each weight.
8. Continue adding weights gradually, recording the water displacement and
submersion depth each time, until the object begins to sink.

Question
(a) How the upthrust is related to the ability of the object to fl oat?
(b) Describe the conditions under which the object fl oats or sinks, based on the
balance between the weight of the object and the upthrust.
The upthrust of the fl oating piece of wood Relationship between upthrust and
is zero. However as the weight of the fl oatation
object increases, the upthrust (or buoyant Upthrust depends on the density of the fl uid.
force) needs to increase for the object If the density of an object is less than that
to remain fl oating, causing more of the of the surrounding fl uid, the object will
object to become submerged. When the fl oat. If the density of the object is larger
weight of the object exceeds the upthrust than the density of the fl uid, the object will
provided by the displaced water, the object sink. This is the reason why an object seems
will begin to sink.

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Physics Form 1 Final.indd 109 16/10/2024 20:56