1). Which law is given by the statement, “Any pressure applied on an enclosed liquid is transmitted equally to all parts.”
i. Pascal’s law ii. Archimedes’ principle iii. Principle of floatation iv. Boyle’s law
Ans: Pascal’s law
2). Which formula shows the ratio of the cross sectional area of two pistons and the forces applied on them in the correct form?
i. A/a = f/F ii. A/a = F/f iii. A/f = a/F iv. F/a = A/F
Ans: ii. A/a = F/f
3).Which of the following formulae can give the part of a solid immersed in a liquid?
i. V1/V2 ii. d1/d2 iii. d2/d3 iv. V2/V3
Ans: ii. d1/d2
4). Which statement is true about the law of floatation?
i. density of the solid is equal to the density of the liquid in which the solid is.
ii. density of the solid is greater than the density of the liquid in which the solid is.
iii. weight of solid is lesser than the upthrust applied on the body by the liquid.
iv weight of solid is equal to the upthrust applied on the body by the liquid.
Ans: iv. weight of solid is equal to the upthrust applied on the body by the liquid.
5). Which statement is true about the law of floatation?
i. upthrust applied on the body is less than the weight of the displaced liquid.
ii. upthrust applied on the body is equal to the weight of the displaced liquid.
iii. upthrust applied on the body is lesser than the density of the liquid.
iv. upthrust applied on the body is equal to the density of the liquid.
Ans: iv. upthrust applied on the body is equal to the density of the liquid.
6). Sarita made a model for presenting Pascal law. But when she pushed one of the pistons inward, the rest pistons did not move outwards. What mistake might she have made in the installation of the apparatus?
i. The syringes are of difference sizes.
ii. The vessel is not of appropriate size.
iii The apparatus is not filled completely with liquid.
iv. The apparatus is not completely airtight.
Ans: iii The apparatus is not filled completely with liquid.
7). Differentiate between:
a). Law of floatation and Archimedes’ principle
| Archimedes’ principle | Law of floatation |
| Archimedes’ Principle explains how objects behave in water or other fluids. | The Law of Flotation is a specific case derived from Archimedes’ Principle |
| It says that when you put something in water, it pushes some water out of the way (displaces it), and this displaced water pushes back on the object | It tells us that a floating object displaces (moves aside) an amount of water that’s equal to its own weight. |
| It’s a general rule that helps us understand why things float or sink in any fluid. | It’s a more focused rule that describes how objects float specifically by displacing their weight in the fluid they are in. |
b). Upward and downward thrust
| Upward thrust | downward thrust |
| Upward thrust is the force that pushes an object from below, making it feel lighter. | Downward thrust is the force that pushes an object from above, making it feel heavier. |
| This force helps objects float and reduces the weight they seem to have. | Gravity is a common example of downward thrust—it pulls everything towards the center of the Earth. |
| It’s like a helpful hand pushing you up when you’re in a swimming pool. | When you drop something, it’s gravity that pulls it down. |
C). Thrust and upthrust
| Thrust | upthrust |
| Thrust is a force that makes things move forward or in a particular direction. | Upthrust, also known as buoyant force, is a force that pushes things upwards when they are in a fluid (like water or air). |
| For example, when a rocket engine propels gases backward, it generates a thrust that propels the rocket forward. | When you’re in a swimming pool, the water pushes you upwards, making you feel lighter. That’s upthrust at work. |
| Thrust helps in moving things, like when you push a swing, you’re giving it a thrust to move. | Upthrust is why objects like boats float in water—it’s like a gentle push from below, helping them stay afloat. |
d). Upward thrust and upthrust
| Upward thrust | Upthrust |
| Upward thrust is the force that pushes something in an upward direction, opposing the force of gravity pulling things down. | Upthrust, also called buoyant force, is the specific upward push experienced by an object submerged in a fluid (like water or air). |
| Imagine jumping off the ground: the force pushing you up is the upward thrust. | When you’re in a pool, the water pushes you upwards, making you feel lighter than usual. This is upthrust in action. |
8). State Pascal’s law.
Ans: Pascal’s law says if you press on a fluid in a closed space, that pressure is transmitted everywhere in the fluid and even to the walls of the container. It’s like a push that spreads out in all directions.
9). Mention two factors which affect pressure due to liquid contained in a vessel.
Ans: Two factors which affect pressure due to liquid contained in a vessel.
Depth: The deeper you go in a liquid, the more pressure there is. It’s like when you dive into a pool, and you feel more pressure as you go deeper.
Density of the Liquid: Thicker or denser liquids can exert more pressure. It’s similar to how a heavy book on your hand feels like more pressure compared to a lighter one.
10). Name any two instruments based on Pascal’s law.
Ans: Any two instrument are :
i) Hydraulic Jack
ii) Hydraulic Brake System
11). State the law of floatation.
Ans: An object will float in a liquid if it is light or less dense than the liquid. Conversely, the object will sink if it is heavier or denser than the liquid.
12). State Archimedes’ principle.
Ans: Archimedes’ principle tells us that when something is put into water or any liquid, it experiences an upward force that helps it float. This force is equal to the weight of the liquid that the object pushes out of the way.
13). While dipping a solid object in a liquid, upthrust on the object due to the liquid and the weight of the displaced liquid are shown to be equal in an experiment. Which principle does the experiment prove?
Ans:This experiment demonstrates Archimedes’ principle. Archimedes’ principle states that when you put an object in a liquid, the upward force (upthrust) on the object is equal to the weight of the liquid that the object pushes aside or displaces. In this experiment, when the upthrust on the object matches the weight of the displaced liquid, it confirms Archimedes’ principle, showing that the liquid’s force pushing up on the object is related to the amount of liquid it displaces.
14). If a freely floating ship has a weight of 5 x 105N, what will be the weight of the water displaced by the ship?
Ans:“If a ship is floating freely, it’s like a dance between the ship’s weight and the weight of the water it pushes aside. The ship weighs 5 x 10^5 Newtons. The weight of the water it moves out of the way (displaces) is also 5 x 10^5 Newtons. It’s like a balancing act in water.”
15). Define upthrust.
Ans: “Upthrust is the gentle push or force that a liquid, like water, gives to an object placed in it. It’s the feeling of being lighter when you’re in the water, and it’s what helps objects float. The more an object pushes the liquid out of the way (displaces it), the stronger the upthrust it experiences
16). Mention a factor that can affect upthrust.
Ans: Certainly, one factor that can affect upthrust is:
Volume or Size of the Object: If you change the size or volume of an object placed in a liquid, it will affect the upthrust it experiences. A larger object will displace more liquid, resulting in a greater upthrust force.
17). What is the role of density in floatation of bodies?
Ans: The role of density in flotation bodies are:
1.Less Dense Objects Float
2.More Dense Objects Sink
18). Mention the factors that affect the upthrust applied on a body.
Ans: The factors that affect the upthrust applied on a body are:
1. Volume of the Body
2. Density of the Fluid
3. Density of the Body
4. Gravity
19.) When a body is fully or partially immersed in a liquid, name the forces acting on
the body.
Ans: When something is in water or any liquid, it’s a battle between gravity pulling the object down and the upthrust from the liquid pushing the object up. If upthrust is stronger, the object floats. If gravity is stronger, the object sinks. If they balance, the object stays where it is in the liquid.
20). State Pascal’s law. Name any two instruments based on Pascal’s law.
Ans: Pascal’s Law: When you push or squeeze a liquid in an enclosed space, that pressure spreads equally everywhere in the liquid.
Two instruments based on Pascal’s Law are:
1. Hydraulic Jack
2. Hydraulic Brakes in Cars
21). How do animals use upthrust in their daily life?
Ans: Floating and Swimming: Fish use upthrust to help them swim and stay afloat in the water. Their bodies are designed to be a bit less dense than water, so they experience an upward push that makes swimming easier.
Staying on the Surface: Some animals, like ducks or water bugs, use upthrust to stay on the water’s surface without sinking. Their bodies and shapes are such that the water’s upthrust force keeps them from going under.
Diving and Surfacing: Marine mammals like seals and whales use upthrust to control their depth in the water. By adjusting their body position and using their lungs to change buoyancy, they can dive down or come up to the surface.
22).Describe the experimental verification of Archimedes’ principle.
Ans: To prove Archimedes’ principle, you can do a fun experiment in your kitchen sink or bathtub:
Gather Your Tools: You need a few things – a measuring cup, a small object (like a toy or a small fruit), and a bathtub or sink filled with water.
Step 1 – Measure the Water: Fill the measuring cup to the top with water and note down the amount.
Step 2 – Check the Object’s Weight: Check the weight of the small object using a scale. Write down the weight.
Step 3 – Sink the Object: Put the small object in the water-filled sink or bathtub. Notice how much water is pushed aside (displaced) by the object.
Step 4 – Measure Displaced Water: Now, take the measuring cup and carefully submerge the object in the water. Measure the water again.
Step 5 – Compare Measurements: Compare the new water measurement with the earlier one. The difference in water levels shows how much water the object displaced
Step 6 – Understand the Result: Archimedes’ principle says the weight of the water displaced by the object should be equal to the weight of the object. If you compare the weight of the water you measured to the weight of the object, you’ll see they’re very close!
This simple experiment proves that the water pushed aside (displaced) by the object weighs the same as the object itself, supporting Archimedes’ principle.
22).How do hydraulic machines help in developmental activities in our country?
Ans: Hydraulic machines are like strong helpers that make tough jobs easier for us. They play a big role in making our country better in many ways:
Construction Work: Imagine huge buildings and bridges being built. Hydraulic machines help lift heavy things like beams and concrete easily. They make construction faster and buildings stronger.
Agriculture: Farmers use hydraulic machines to do tasks like lifting heavy loads, plowing fields, and digging. This helps them grow more crops and food for everyone.
Waste Management: Hydraulic machines help pick up and move big bins of trash. This keeps our cities clean and helps manage waste properly.
Mining: In mines, hydraulic machines help dig deep into the Earth to find valuable minerals and resources. This is important for industries and the economy.
Transportation: Some vehicles, like buses and trucks, use hydraulics for brakes and steering. This makes driving safer and smoother.
23). Illustrate that hydraulic machines are force magnifiers.
Ans:let’s break down the concept of hydraulic machines as force magnifiers in simple terms:
In a hydraulic machine, when you press that button or lever, it pushes a small amount of liquid (like oil) into a narrow tube. This narrow tube then pushes a bigger piston (a big part of the machine) with a lot more power because the pressure is spread over a larger area.So, with a little push, you can move or lift something much heavier using a hydraulic machine. It’s like having a magical strength-booster!
24). How does a hydraulic garage lift function? Explain with an illustration.
Ans: A hydraulic garage lift is like a super-strong table that can go up and down, helping fix cars and trucks easily. Here’s how it works:
The Pumping Action: Imagine you have a bike pump. When you press down the pump, it pushes air into a tire and makes it hard. In a garage lift, there’s a pump that’s usually operated by hand or electricity.
Pushing the Oil: Instead of air, the pump pushes a special liquid, often oil, through a pipe. This liquid goes into a narrow tube, like a straw, and pushes against a bigger plate (piston) at the other end.
Multiplying the Force: Just like pressing on a small area of a seesaw can move a much heavier person on the other end, pushing a small amount of liquid into a narrow tube pushes a bigger piston with a lot more power.
Lifting the Platform: This powerful push lifts the platform of the garage lift, which is where the car or truck goes. The platform can go up to a certain height, allowing mechanics to work underneath the vehicle.
24). It is easier to pull a bucket of water from a well until it is inside the water but it is difficult to lift the bucket when it is out of water.
Ans: Pulling a bucket of water inside a well is easier because water helps lighten the bucket, making it feel lighter. However, lifting the bucket out of the water is harder as you’re carrying both the weight of the bucket and the water inside without any support. Water provides a lifting boost when the bucket is submerged.
25). A bucket of water is filled faster in the downstair’s tap than in the upstair’s tap.
Ans: Filling a bucket downstairs is faster than upstairs because gravity helps pull the water downwards, making it flow faster. Upstairs, the water has to fight gravity, slowing down the filling process. It’s like going down a slide versus climbing up; it’s faster and easier going down.
26). The blood pressure in human body is greater at the feet than at the brain.
Ans: Blood pressure is higher at the feet than at the brain because our hearts need to pump harder against gravity to push blood up to the brain. It’s like pushing a ball uphill—it takes more effort. The blood vessels also help by squeezing and pushing the blood upwards, but gravity makes it a bit harder for the blood to reach the brain, so the pressure is higher at the feet.
27). Deep-sea divers wear diving suits.
Ans: Deep-sea divers wear diving suits to stay safe and comfortable underwater. The suits keep them warm because the deep sea is cold. They also protect their bodies from cuts, stings, and other dangers in the water. Additionally, the suits help them float and control their movement, making it easier to dive and explore the deep ocean. It’s like having a special outfit that keeps them safe and cozy in the underwater world.
28). An egg floats on saturated salt solution.
Ans: An egg floats in salty water because the salt makes the water heavier and denser than the egg. This extra weight pushes the egg up, making it float.
29). An iron nail sinks in water but a ship made of the same material floats on it.
Ans: An iron nail is small and heavy, so it sinks in water. But a big ship made of iron floats because it’s designed to spread its weight over a large area, like a big metal boat, so it can stay on top of the water.
30). It is easier to swim in ocean than in a river.
Ans: Swimming in the ocean is easier than in a river because the ocean is big and has less pushy water compared to rivers. Rivers can push you more, making it harder to swim.
31). Dead bodies float on water only after some time.
Ans: Dead bodies float on water after some time because as the body starts to decompose, gases like methane and bacteria build up inside the body, making it less dense. This makes the body float on the water instead of sinking.
32). Hydraulic machines are also named as force magnifiers.
Ans: Hydraulic machines are called force magnifiers because they help us use a small force to move a much bigger force. It’s like getting more power to lift or move heavy things by using water or another fluid to amplify our strength.
33). Aeroplanes cannot fly on the surface of the moon.
Ans: Airplanes can’t fly on the moon’s surface because the moon doesn’t have air like our Earth does. Airplanes need air to generate lift and move, but there’s no air on the moon, so they can’t fly there.
34). A balloon filled with helium does not rise up in the air indefinitely.
Ans: A balloon filled with helium doesn’t keep going up forever because the helium makes the balloon lighter, but there’s a point where the air outside the balloon is also light enough. At that point, the balloon stops going up and stays at a certain level in the sky.
35). A loaded ship sinks more than an empty ship.
Ans: A loaded ship sinks more than an empty ship because the things (cargo, items) on the loaded ship make it heavier, and heavy things sink deeper in the water.
36). Ice floats on water.
Ans: Ice floats on water because it’s lighter than water. When water freezes into ice, it becomes less dense, which means it takes up more space and is lighter. That’s why ice floats on the surface of water.
37). An iron nail sinks in water but floats on mercury.
ans: An iron nail sinks in water because it’s heavy and denser than water. However, it can float on mercury because mercury is even denser than the iron nail, making the nail less dense than the mercury and allowing it to float.
38). The size of an air bubble increases when it comes up and up in water
Ans: The air bubble gets bigger as it goes up in water because there’s less squishing pressure from the water, so the air inside the bubble expands and makes it larger.
39). The weight of a piece of stone, when fully immersed in water, is 18 N and it 4 N of displaces water, What is the we the weight of the stone in air?
Ans:To find the weight of the stone in air, we’ll use the principle of buoyancy.
The weight of the stone in air is equal to the weight of the stone in water plus the weight of the water displaced by the stone.
Weight of stone in water = 18 N
Weight of water displaced by the stone = 4 N
So,
weight of the stone in air = Weight of stone in water + Weight of water displaced
= 18 N + 4 N
= 22 N
Therefore, the weight of the stone in air is 22 N.
40). A cube of wood, whose volume is 0.2 m³ and density 600 kg/m³, is placed in a liquid of density 800 kg/m³. What fraction of the volume of the wood be immersed in the liquid?
Ans: Solution:
Given:
Density of wood :(600 kg/m³)
Density of liquid :(800 kg/m³)
Volume of the wood: (0.2 m³)
We’ll calculate the fraction (F) of the volume of the wood cube immersed in the liquid:
F = Density of wood / Density of liquid
F = 600 kg/m³ / 800 kg/m³
F = 3/4
So, 3/4 or 75% of the volume of the wood cube will be immersed in the liquid.
