Activity 1 1. Fill a plastic bag with water and poke several holes in

various part of it with needles. Squeeze the plastic bag gently from the top. Observations: ________________________________________________

Conclusion: __________________________________________

2. Prepare a tall plastic bottle with a few holes at different heights. Seal the holes with plasticine and fill the bottle with water. Remove the plasticine from the holes simultaneously and observe the flow of water out of the holes.

Make a sketch to show the flow of water from the holes.

3.2

What is Pressure in Liquids?

A liquid in a container exerts pressure because of its ____________. For example, if you try to put your finger over the end of a tap when it is turned on, you can feel the pressure of the water in the pipe. Pressure in liquid acts in all _______________.

(a) What is the relationship between the pressure of water and the distance of

its flow from the holes?

________________________________________________________________

(b) What is the relationship between pressure of water and its depth?

3. Lower the thistle funnel slowly into

the water to a depth, h = 50 cm and the manometer reading l is measured. Repeat with different liquid i.e. alcohol and sea water.

(a) Which of the three liquids has the

highest pressure at the same depth? Which liquid has the lowest pressure?

________________________

(b) What is the relationship between the density of a liquid to its pressure? ________________________________________________________________

Relate depth to pressure in liquid

The pressure in a liquid is _________ proportional to the depth. The pressure in a liquid __________ with depth.

State the pressure in liquid formula

The container on the right has a base area A. It is filled to a depth h with a liquid of density ρ. Calculate: (a) volume of liquid = (b) mass of liquid = (c) weight of liquid = (d) force on base = (e) pressure =

At a depth h in a liquid of density ρ : Pressure = Where ρ = g = h = Derive unit for pressure in liquid:

Relate density to pressure in liquid

The pressure in a liquid is __________ proportional to the density of the liquid.

1. If the density of water is 1000 kg m-3, what is the pressure due to the water at the bottom of a swimming pool 2 m deep?

2. Given that the density of mercury is 13 600 kg m-3. Calculate the pressure of mercury at a point 40 cm from the mercury surface.

3. The figure shows a cross section of a dam. The density of water in the dam is 1000 kg m-3. The pressure exerted by the water at X is …….

4. A deep- sea diver is wearing a watch that can withstand a maximum pressure of 4.5 x 106 Pa due to the sea water. [Density of the sea water = 1030 kg m-3 , g = 10 N kg-1] (a) Calculate the maximum depth

the diver can dive without spoiling the watch.

(b) If the surface area of the glass

of the watch is 9.0 cm2 , calculate the force acting on the glass of the watch due to the sea water at a depth of 100 m.

Solve problems involving pressure in liquids

5. In the diagram on the right: (a) How does the pressure at A

compare with the pressure at B?

(b) How does the pressure at B compare with the pressure at D?

(c) How does the pressure at A

compare with the pressure at C? (d) Calculate the pressure at B due to

the water.

(e) If the water in the system were

replaced with paraffin, how would this affect the pressure at B?

6. The figure shows a bottle filled with 40 cm height of liquid A and 70 cm height of liquid B. The densities of liquid A and liquid B are 1000 kg m-3 and 2500 kg m-3 respectively. What is the pressure of (a) liquid A at point P? (b) liquid A and liquid B at point Q?

1. Dam holds water at high altitude. The wall of the dam has to be thicker at the base than at the top because it must withstand the __________ pressure in depths of the water.

Describe the applications of pressure in liquids

2. Water is stored in water tank at higher level so as to supply water at __________ pressure.

3. Submarine is built with thick wall so as to withstand enormous pressure at _________ depth.

4. A patient receiving intravenous drips of a certain fluid from a bottle. In order for the fluid to flow into the vein, the bottle must be placed at a height above the injection site so it has __________ pressure to flow into the veins of the patient.

5. (a) Figure (a) shows a container of herbal tea. Explain why the tea flows out of the tap at a fast speed.

(b) Explain why when there is very little tea left in the container, it is easier for the tea to flow out of the tap when the container is tilted as shown in figure (b).

6. Why does the water pressure from a tap at the top floor is lower than the water pressure from a tap at the bottom floor of an apartment?

[SM SAINS MUZAFFAR SYAH]]

TUTORIAL 3.2 1. An air bubble is at a depth of 5 m

below the surface of a lake . What is the pressure of water on the bubble if the density of the water is 1 000 kg m-3? A. 5 x 10-3 Pa

B. 2 x 10 2 Pa C. 5 x 10 3 Pa D. 5 x 104 Pa 2. The figure shows a high tin with a

length of 100 cm is filled to the full with water.

If the pressure caused by the

water at point P is 8000 Pa, What is the value of L? (Density of water = 1000 kg m - 3 ) A 10 cm B 20 cm C 60 cm D 80 cm

3. Which one of the following is not

true? A The pressure in a liquid

increases with depth B The pressure in a liquid

increases with density of the water

C The pressure in a liquid increases with area of contact

D The pressure in a liquid increases with the gravitational acceleration

4. The figures show liquids in containers. Which column of liquid exerts the greatest pressure on the base of its container?

5. The figure shows a polystyrene

block being pushed to a depth of h cm from the water surface. P is the water pressure acting on surface Q.

Which graph shows the

relationship between P and h when the block is pushed deeper into the water? (2005)

[SM SAINS MUZAFFAR SYAH]]

6. The figure shows three containers with different shapes filled with water with the same level. The pressure caused by the water at point P , Q and R are P1 , P2 and P3 respectively.

Which comparison is correct?

A P1 > P2 > P3 B P1 < P2 < P3 C P1=P2 = P3

7. Equal masses of water are poured

into four jars as shown. In which jar is the pressure exerted by the water on the base the greatest?

8. The figure shows three wooden

blocks J,K and L are pressed into the water until the base of its reach at level P. The pressure caused by the water at base of the wooden blocks J , K and L are X1 , X2 and X3 respectively.

Which comparison is correct?

A X1 > X2 > X3 B X1 < X2 < X3 C X1=X2 = X3

9. The figure shows a siphon

system.

Which of the following is true? A Water in beaker A flows into

beaker B until the volume of water in beaker A is the same as the volume of water in beaker B

B Water in beaker A flows into beaker B until the level of water in beaker A is the same as the level of water in beaker B

C Water in beaker A flows into beaker B until beaker B is full

D Water in beaker A flows into beaker B until beaker B is empty

[SM SAINS MUZAFFAR SYAH]]

10. Diagram below shows the process of supplying water from a water tank on a hill to a water tank X on a tall building.

Calculate the pressure of the water at X. [Density of water = 1000 kgm-3] (2006) A. 1.4 x 105 N m-2 B. 1.6 x 105 N m-2 C. 2.6 x 105 N m-2 D. 3.0 x 105 N m-2

11. Diagram below shows a fish in the

sea.

What is the pressure exerted by the water on the fish? (2007) [water density = 1 000 kgm-3] A. 6 x 10-3 Pa B. 6 x 101 Pa C. 6 x 103 Pa D. 6 x 104 Pa

13. The wall of a dam is much thicker at the bottom than at the top because A pressure of water at the upper

level is higher than pressure of water at the deeper level

B pressure of water at the upper level is lower than pressure of water at the deeper level

C pressure of water at the upper level is the same as than pressure of water at the deeper level

14. Diagram 7 shows two identical

containers containing liquid P and liquid Q.

When the height of liquid P is 15 cm and the height of liquid Q is 20 cm, water spurt is the same. The density of liquid P is 2.0 g cm-3. What is the density of liquid Q? (2008) A. 0.67 g cm-3 B. 1.30 g cm-3 C. 1.50 g cm-3 D. 2.70 g cm-3

[SM SAINS MUZAFFAR SYAH]]

15. Diagram 10 shows the water piping system of a house.

What is the water pressure in the

tap? Density of water = 1 000 kg m-3 and atmospheric pressure = 1.0 x 105 Pa. (2008) A. 8.0 x 103 Pa B. 5.8 x 104 Pa C. 1.08 x 105 Pa D. 1.58 x 105 Pa

16. Diagram 8 shows two divers in a

lake and a diver in a sea. The pressure of water at T, S and U is PT , PS and PU respectively.

Diagram 8

Which of the following comparisons is correct about the pressure exerted on the divers? A. Pu > PT > PS

B. Pu < PT < PS C. Pu = PT > PS D. Pu = PT < PS

17. Diagram 9 shows water spurting

out from a container at different depths.

Diagram 9

Which graph shows the correct relationship between the pressure exerted by the water, p and the depth of the water, h?

[SM SAINS MUZAFFAR SYAH]]

1. Question 2: Kelantan 10 Diagram 2.1 shows two different containers filled with water. The water pressure at point P and point Q are the same.

(a) What is the meaning of pressure? .........................................................

[1 mark] (b) State one factor that affect the

water pressure at point P and Q. ..........................................................

[1 mark]

(c) Calculate the water pressure at point P.

[Density of water = 1000 kgm-3] [2 marks]

(d) Diagram 2.2 shows the water spurt when a hole is made near the base of container B.

Diagram 2.2

Diagram 2.3 shows the water in container B is replaced by liquid X which has higher density than water.

Diagram 2.3 Sketch the spurt of liquid X in Diagram 2.3.

[1 mark]

[SM SAINS MUZAFFAR SYAH]]

2. SPM 2007 paper 2 A2 Diagram 2 shows a water tank that supplies water to a block of flats. The water flows to each unit of the flat due to water pressure.

a. What is meant by pressure?

...........................................................

[1 m]

b. A water tank with a height of 3.0 m is fully filled with water. Calculate the water pressure at the base of the water tank. [Density of water = 1 000 kgm-3]

[2 m]

c. Based on Diagram 2, compare the water pressure at P and at Q. Explain your answer. ..........................................................

[2 m]