## Tuesday, November 16, 2010

### SPM Trial MARA 2010 ~ paper 2 ( Water tank )

Question 7

Diagram 7 shows a public water tank which supplies water for domestic use to a residential area.
Rajah 7 menunjukkan sebuah tangki air awam yang membekalkan air untuk kegunaan domestik di satu kawasan perumahan.

(a)
State one factor which affects pressure in a liquid.
Nyatakan satu faktor yang mempengaruhi tekanan dalam cecair.
Hits for solving problem :
Liquid pressure increase with depth//height, and increase with density.
(b)
Based on Diagram 7, calculate the water pressure at X.
(Density of water = 103 kg m-3).
Berdasarkan Rajah 7, hitungkan tekanan air di X.
( Ketumpatan air =103 kg m-3).
Hits for solving the problem:
~ list all info given or underline the importance information given.
Given ρ, g ,h and find P .
~ state the formula, P = ρ g h
~ substitute the value for each quantity
~ answer with the correct unit.

(c)
Tenants on the fifth floor of the apartment block are unable to obtain tap
water. Why?
Penghuni di tingkat lima blok pangsapuri tidak menerima bekalan air paip. Mengapa?

(d)
Suggest and explain modifications to the water distribution system shown in Diagram 7, to ensure the following :
Tangki air itu tidak dapat memenuhi keperluan semua penghuni di blok pangsapuri lima tingkat. Cadang dan terangkan pengubahsuaian yang perlu dilakukan untuk setiap yang berikut:

(i)
Sufficient water supply for all area residents.
Bekalan air yang mencukupi untuk semua penghuni kawasan.

(ii)
Water supply reaches the fifth floor of the apartment building.
Bekalan air boleh sampai ke tingkat lima blok pangsapuri.

e)
The public water supply system often faces a problem in delivering water to water tanks located on tall buildings.
Suggest and explain one other way to overcome this problem.
Sistem bekalan air awam kerapkali menghadapi masalah untuk menyalurkan air ke tangki
air yang berada di bahagian atas bangunan tinggi.
Hits for solving problem (c) - (e):
In prublic water supply system, the water is pumped up to a water tank located higher than the building in that area.
Due to the gravitational pull, water in the storage tank is maintaned at a high pressure and enables water to flow to the lower area ( consumers )

a) The height of water tank.
b)
P = ρ g h
= 1000 x 10 x 10
= 100 000 N/ m
= 100 000 Pa

c)
Water tanks are tall to provide pressure.
The location of fifth floor apartment is exceed the height that the tank's water pressure can handle.

d)
i) Build a larger water tank,to holds enough water for all area residents.
ii) Ensure water tank located higher than apartment , to provide the necessary pressure.

e) Install a pump to provide pressure.