Pressure
1. Choose the correct answer:
a) Lactometer is based on which principle?
(i) Pascal's law
(ii) Archimedes principle
(iii) Law of Gravitation
(iv) Newton principle
b) What is the state of hydrogen balloon going up into the atmosphere?
(i) Bellunco weight Displaced air weight
(ii) Balloon Weight > Displaced Air Weight
(iii) Balloon weight volume of air displaced
(iv) Bellunco weight < Displaced air weight
c) In a hydraulic machine, if the cross-sectional area of the larger piston is twice that of the smaller piston, what is signatures of the weight (W1) on the smaller piston and the weight (W2) on the larger piston to keep the machine in equilibrium?
(i) W * 1 = 4N_{c} W * 2 = 2N
(ii) W * 1 = 5N , WZ = 10N
(iii) W * 1 = 2N , W * 2 = 1N
(iv) W * 1 = 3N , W * 2 = 1.5N
d) The weights of an object suspended in air, water and glycerine on a spring balance are W1, vely. What is the order of signatures based on increasing weight?
(i) W1 W2 W3
(ii) W2W1W3
(iii) W3W1 W2
(iv) W3W2W1
e) When a ship enters a river from the sea, it is found to be submerged more than t is the reason for this?
(i) The temperature of sea water is higher than that of river water.
(ii) Density of sea water is higher than that of river water.
(iii) The temperature of sea water is lower than that of river water.
(iv) Density of sea water is less than that of river water.
(f) What is the signature of the force shown in the diagram for the force ex the arm pushing through the water?
(i) Equal pressure is exerted on all parts of a force.
(ii) The more the force pushes inward from the surface of the water, the more the upward pressure increases.
(iii) Forced water pressure only moves upwards.
(iv) The buoyant pressure on the water increases until the force completely sinks into the surface of the water.
g) If a cubical box made of two different materials is kept in water and exerts equal vertical pressure on them, then what quantity is equal in both the two sides?
(i) Density
(ii) Weighing
(iii) Volume
(iv) mass
h) What is the upward pressure exerted on the crucible shown in the figure?
(i) 3N
(ii) 4N
(iii) 5N
(iv) 1N
2. Write the difference between:
Arc | Vertical Pressure |
An arc is a part of a curve, usually a circle or any curved line. | Vertical pressure refers to the force that acts straight up or down, often due to weight or gravity. |
In physics, it can refer to the path something follows when moving along a curved route. | It is the pressure applied in a vertical direction, like the weight of something pressing down. |
Panama Steelco Pin Slinking Action | Panama Steel Plate Floating Action |
This refers to a specific mechanism or action where the pin or connecting parts move or slide in a particular manner to help with mechanical movements. | This refers to a system where a steel plate is designed to "float" or move freely, usually in a way that allows for more flexibility or adjustment. |
It's often used in systems that require controlled, precise motion. | It might be used in settings where the steel plate needs to absorb pressure or adapt to varying conditions without being fixed in place. |
Sinking a Hot Air Balloon | Flying a Hot Air Balloon |
Sinking refers to the process of descending the hot air balloon to the ground. | Flying refers to the process of ascending or staying afloat in the air. |
To sink, the pilot lowers the temperature of the air inside the balloon or releases some hot air, causing it to lose buoyancy and come down. | To fly, the pilot heats the air inside the balloon, making it less dense than the surrounding air, causing the balloon to rise. |
3. Give reasons of the following:
a) A special type of oil is used in hydraulic brakes.
Ans: The oil used in hydraulic brakes has to be transferred against a very high pressure. A special type of hydraulic brake oil is used to resist the heat generated during this process, reduce internal friction and maintain the effectiveness and safety of the hydraulic brake system.
b) If a lump of wood is dropped under the surface of water by applying finger force, the lump immediately floats to the surface.
Ans: Density of wood is less than density of water. Therefore, the pressure exerted by the crab is greater than the crab's weight. As a result, the force of gravity neutralizes the upward pressure. Even if such a piece of wood is submerged under the surface of the water by applying finger force, it immediately floats to the surface.
c) Why do we feel light when floating in water?
Ans: e feel light in water because the water pushes us up. This helps balance our weight and makes us feel lighter than on land.
d) A bucket full of water sinking in a bucket feels lighter when the weight is raised inside the water, but feels heavier when the weight is taken out of the water.
Ans: As long as the magma is submerged in water, the upward pressure of the water is exerted on it. So as soon as you take it out of the water, the weight increases equal to the upward pressure on the magma, so you feel heavy when you take it out of the water.
e) Density of water in dead sea is 1240 kg/m3. Swimming in the Dead Sea is much easier than in a swimming pool.
Ans: Dead sea water is more dense than swimming pool water. Therefore, dead sea water exerts more upward pressure than swimming pool water. Therefore swimming in the Dead Sea is much easier than swimming.
f) If there are more passengers than the maximum number of passengers that can be floated in the boat, there is a possibility of the said boat sinking.
Ans: If the boat carries more than the maximum number of passengers, the boat will not be able to displace its own weight in water, thereby causing the boat to sink.
4. Answer the following questions:
a) Write Pascal's Law.
Ans: If a pressure is applied to a liquid in a closed vessel at one point, the same propagates longitudinally in all directions.
b) Write two points of utility of Pascal's rule in daily life.
Ans: Following are the two uses of Pascal's rule in daily life.
(i)Based on Pascal's law, a hydraulic car lift can be used to raise the car.
(ii) Hydraulic brakes used in vehicles are made based on Pascal's law.
c) What is hydraulic machine?
Ans: A hydraulic machine is a force increasing device based on Pascal's law.
d) Write Archimedes principle.
Ans: Archimedes' principle: “When an object is partially or completely immersed in a liquid, the liquid exerts an upward pressure on the object equal to the weight of the liquid displaced.”
e) What is vertical pressure?
Ans: The force which pushes the object upwards while keeping the object at a level is called upward pressure. When an object is partially or completely immersed in a gas or liquid, the upward force exerted on the said object is called upward pressure.
f) State the force exerted on the floating object with its direction.
Ans: Upthrust is the force exerted on the floating mass. This force direction is upward.
g) Write the rule of floats.
Ans: An object in a liquid displaces an equal amount of its weight in the liquid. This is called the Law of Floatation.
h) Write any two applications of Archimedes principle.
Ans: Following are some two applications of Archimedes' principle.
(i)The density of liquids can be measured by making a hydrometer.
(ii)Ship, boat etc, can be built and the load that can be carried by the tool can be calculated.
i) Mention a unique method of demonstrating positive pressure in liquids and gases using available materials.
Ans: Method of showing positive pressure in a liquid:
First measure the weight of a stone with a spring balance on a thread and again take the weight of
Method of demonstrating the positive pressure exerted on a gas:
A balloon filled with helium gas goes up when the air is released. This is when the air is pressed upwards.
j) Explain with illustration the cause of upward pressure when a substance is kept in a liquid.
Ans: When an object is placed in a liquid, the liquid tends to displace the liquid. Where the force applied to the e right surface is applied to the left surface. The force applied to the front surface cancels the force applied to the rear surface. So the force from the lower surface cannot be canceled by the force from the upper surface. The force exerted by the lower surface is always greater, so the fluid exerts upward pressure due to the force exerted by the mass or the pressure difference.
k) A stone sinks when dropped in water. Did the said stone sink without being subjected to upward pressure? Write with logic.
Ans: When upward pressure is exerted on the stone, the weight t of the displaced water stone sinks when water is dropped even if it is subjected to an upward pressure. is less than the weight of the stone. That is, gravity cannot neutralize the upward pressure in this process. That is why the said stone sinks when water is dropped even if it it subjected to an upward pressure.
l) Substances whose density is greater than the density of the liquid sinks in the said liquid. Is this statement completely true? Confirm with example.
Ans: Generally this statement is completely true. Because substances with a density greater than the density of a liquid cannot displace a liquid equal to its weight. Thus those substances sink in the said liquid. For example, a rock made of iron has a higher density than water, so the iron rock sinks in water.
m) Two identical balloons are filled equally with one air and one hydrogen. What is the difference between the two balloons when they are released? Explain with reasons.
Ans: The average density of a balloon filled with hydrogen is less than the density of air. A decrease in density can displace air equal to its own weight, causing the air to float or rise. So the average density of a balloon filled with air is more than the density of air. If it cannot displace air equal to its weight, it sinks or sinks from the place where the air is left.
n) An object is floating just below the surface of water. If the water dissolves, then what changes in the state of the said object? Explain with reasons.
Ans: If the water dissolves, the density of the water increases, and the matter that floats just below the surface of the water rises into the water. Because as the salt dissolves, the density of the water becomes greater than the density of the substance.
o) How many digits are shown on the scale needle shown in figure (a) and (d)? Mention with reason.
Answer: The vessel in figure (a) is not filled with liquid, but the first vessel is 20N. Therefore, when 5N and BN weights are added respectively, the needle of the measuring needle shows 25N and 28N respectively, while in figure (a) the first container is full of liquid (30N). Therefore, when 5N and 8N weights are added respectively, the same weight of liquid is displaced and the needle of the weighing gauge shows 30N and 30N respectively.
p) When a man was milking a lactometer, its narrow stem got completely submerged in the milk. What conclusions can be drawn from this?
Answer: If the lactometer is filled with milk, its narrow stem part is immersed in the milk, then it can be concluded that the density of the said milk is low. This means that milk contains more water and less milk.
