Question
(a) Fig. 1.1 shows a piece of glass of thickness 2.0 cm and area 0.15 m2.
The density of the glass is 2.6
kg/
.
Calculate the weight of the piece of glass.
weight = ……………………………………….. [3]
(b) The piece of glass shown in Fig. 1.1 is used as the vertical viewing window of an aquarium.
The atmospheric pressure outside the aquarium is 1.0 × 
Pa. The average pressure on the inside of the
aquarium window is 1.3 × Pa.
Calculate the resultant force acting on the window due to these pressures and state the direction in which it acts.
force = …………………………………………………..
direction of force …………………………………………………….. [4]
(c) Fig. 1.2 shows a vacuum pump connected to the top of a vertical tube with its lower end
immersed in a tank of liquid. The pump reduces the pressure above the column to zero and the
pressure at point X is 9.6 × 
Pa.
Calculate the density of the liquid.
density = ………………………………………… [3] [Total: 10]
Answer/Explanation
Ans:
(a)
m=ρ V
OR
ρ = m / V in any form
W = mg =78 N
(b)
4.5 × 
N
F= ΔPA
OR
P = F / A in any form (ΔP = 1.3 × 
– 1.0 × = ) 3 × 
outwards
(c)
ρ=800 kg / m3
ρ= P / gh
OR
P= ρgh in any form
ρ= 9.6 × 
/ (10 × 12)