Page 55 - Physics Form 5 KSSM_Neat

Figure 2.6 shows a CHAPTER 2
U-tube filled with liquid
X. Then it is added with Pressure
liquid Y which does not
mix with liquid X. This h 1
apparatus can be used to h 2 Liquid Y
KEMENTERIAN PENDIDIKAN MALAYSIA
compare the densities of A B
two immiscible liquids. Liquid X
Liquid X

Figure 2.6 A U-tube filled with liquid X and liquid Y
Liquid pressure at point A, P = h ρ g, where ρ = density of liquid X
1
1
1
1
Liquid pressure at point B, P = h ρ g, where ρ = density of liquid Y
2
2
2
2
Since points A and B are at the same level and both liquids are static,
pressure at point A = pressure at point B
P = P 2
1
h ρ g = h ρ g
1
2
2
1
Therefore, h ρ = h ρ
1 1 2 2
The values of h and h can be measured with a metre rule. If the density of liquid X, ρ is
1
1
2
known, the density of liquid Y, ρ can be calculated and vice versa.
2
Solving Problems Involving Pressure in Liquids Info
The formula P = hρg is used to calculate the pressure at a depth At sea level, atmospheric pressure
in a liquid. The surface of the liquid also experiences pressure. has a value of about 100 000 Pa,
or 100 kPa.
Therefore, the actual pressure experienced by an object in a
liquid is calculated with the following formula.
LET’S ANSWER
LET’S ANSWER
Actual pressure = hρg + P , where P = atmospheric pressure
atm atm
http://bit.ly/
Example 1 2QFcNcV
Figure 2.7 shows a fish is at a depth of 1.5 m in an
aquarium. The density of water in the aquarium is
1 050 kg m and atmospheric pressure is 100 kPa. Depth
–3
= 1.5 m
[Gravitational acceleration, g = 9.81 m s ]
–2
(a) What is the pressure experienced by the fish
caused by the water around it?
(b) Calculate the actual pressure acting on the fish.

Figure 2.7

LS 2.1.2 2.1.3 45