Page 126 - Physics
P. 126
Physics for Secondary Schools
(a) Why the two objects which were 11. A hot-air balloon including the
initially balanced in air, appear envelope, gondola, burner fuel and
imbalanced when immersed in one passenger has a total mass of 450
water? kg. The air outside the balloon is at
(b) Which object has the higher 20 °C and has a density of 1.29
density? Explain your answer. kg/m . The air inside the envelope is
3
9. When an object of mass 200 g is heated to a temperature of 120 °C,
submerged in the methanol, its at which it has a density of 0.90 kg/
apparent weight is 1.052 N. When m . What volume must the envelope
3
submerged in benzene, its apparent expand in order to lift the balloon
weight is 0.951 N. If the density of into the air?
methanol is 0.8 g/cm , what is the
3
density of benzene? 12. A salvage ship is attempting to raise
an iron anchor off the ocean fl oor.
10. To measure the density of a 100 g The anchor has a mass of 560 kg
block of wood, a 100 g lead sinker and the density of iron is 7 800 kg/
is attached to make the block sink as m . The cable used to lift the anchor
3
shown in Figure 5.19. When lowered can support a weight of 5 000 N
into the water, the combination has before breaking. Use 1 025 kg/m 3
an apparent weight of 1.3 N. If the as the density of seawater.
3
density of lead is 11.3 g/cm , what (a) Can the cable support the
is the density of the wood? anchor while it is completely
submerged?
(b) Can the cable support the anchor
when it is completely out of the
2.0 N 1.3 N water?
(c) What percentage of the anchor
will be out of the water when
the cable breaks?
13. Icebergs are hazardous to shipping
Block because so much of their volume is
of wood below the water level. If the density
3
of seawater is 1 025 kg/m and the
Water
3
density of ice is 919 kg/m , what
percentage of an iceberg is below
Lead sinker
the water level?
Figure 5.19
120
Student’s Book Form One
Physics Form 1 Final.indd 120 16/10/2024 20:57
