- (a) decreases
- (b) increases
- (c) remains same
- (d) may increase or decrease
Answer:
(b) increases
Pressure decreases upward, so the air bubble expands.
- (a) density
- (b) pressure
- (c) velocity
- (d) mass
Answer:
(a) density
- (a) increased pressure lowers the boiling point
- (b) increased pressure raises the boiling point
- (c) decreased pressure raises the boiling point
- (d) increased pressure lowers the melting point
Answer:
(b) increased pressure raises the boiling point
- (a) more liquid is displaced
- (b) more weight of liquid is displaced
- (c) pressure increases with depth
- (d) All the above
Answer:
(c) pressure increases with depth
- The weight of a body immersed in a liquid appears to be less than its actual weight.
- The instrument used to measure atmospheric pressure is barometer.
- The magnitude of buoyant force acting on an object depends on the density of the liquid.
- A drinking straw works because of atmospheric pressure.
If false, correct the statement.
Answer: True
Answer: False
Correct Statement:
The density of an object determines whether it floats or sinks.
Answer: False
Correct Statement:
Wide foundations reduce pressure on the ground.
Answer: True
Answer: True
| List I | List II |
|---|---|
| Density | Mass / Volume |
| 1 gwt | 980 dyne |
| Pascal’s law | Pressure |
| Pressure exerted by fluid | (h\rho g) |
| Lactometer | Milk |
Answer:
Liquid pressure depends on:
- Depth of liquid
- Density of liquid
- Acceleration due to gravity
Answer:
Helium is less dense than air, so the buoyant force acting on the balloon is greater than its weight.
Answer:
Sea water contains salts and has greater density than river water. Hence, sea water provides greater buoyant force, making swimming easier.
Correction applied:
Original question wording was misleading.
Answer:
The pressure exerted by the weight of the atmosphere on Earth is called atmospheric pressure.
Answer:
Pressure applied on an enclosed incompressible liquid is transmitted equally in all directions throughout the liquid.
Explanation:
Pressure is given by:
Where:
- (P) = Pressure
- (F) = Force
- (A) = Area
When the same force acts on a smaller area, pressure increases.
Example:
A nail has:
- a pointed end (small area)
- a flat head (large area)
The pointed end easily penetrates wood because pressure is greater at smaller area.
Construction
A mercury barometer consists of:
- A long glass tube closed at one end
- Mercury filled inside the tube
- A trough containing mercury
Working
- Atmospheric pressure acts on mercury in the trough.
- Mercury rises in the tube until pressure balances.
- Height of mercury column measures atmospheric pressure.
Standard atmospheric pressure:
Answer:
- If object density < liquid density → object floats
- If object density > liquid density → object sinks
Examples:
| Object | Result |
|---|---|
| Wood in water | Floats |
| Stone in water | Sinks |
Construction
A hydrometer has:
- Cylindrical stem
- Spherical bulb at lower end
- Lead shots or mercury inside bulb
- Narrow graduated tube
Working
- Hydrometer is placed in liquid.
- It floats vertically.
- Reading at liquid surface gives relative density.
Laws:
- A floating body displaces liquid equal to its own weight.
- Centre of gravity and centre of buoyancy lie in the same vertical line.
Assertion:
A floating body displaces liquid equal to its own weight.
Reason:
Then the body experiences no net downward force.
Answer:
(a) Both are true and reason correctly explains assertion.
Assertion:
Pascal’s law is the principle behind hydraulic lift.
Reason:
Pressure is thrust per unit area.
Answer:
(b) Both are true but reason is not correct explanation.
Given:
- Weight of block = 200 g
- Volume = (300 cm^3)
Correct Concept:
For a floating body:
Therefore,
Correction made:
Original solution incorrectly used volume as upthrust.
Given:
Given:
Conversion:
Given:
Weight in air = 100 gwt
Since wood floats:
Thus,
Correction made:
Original answer was conceptually incorrect.
Given:
Using:
Answer:
Fish use swim bladders filled with gases.
- Increasing gas volume decreases density → fish rises.
- Releasing gas increases density → fish sinks.
Observation:
| Liquid | Result |
|---|---|
| Water | Ice floats |
| Alcohol | Ice sinks |
Reason:
Answer:
- Water enters through hole.
- Weight of boat increases.
- Boat cannot displace enough water.
- Buoyant force becomes insufficient.
- Boat sinks.
Effect of Area on Pressure
Observation:
- Standing on sand → feet sink deeper
- Lying down → body sinks less
Conclusion:
Pressure increases when area decreases.
Water Exerts Pressure
Observation:
Balloon tied at pipe bottom bulges outward.
Conclusion:
Water exerts pressure on bottom of container.
Pressure Increases with Depth
Observation:
Water from lower holes flows faster.
Conclusion:
Pressure increases with depth.
Pressure Depends on Density
Observation:
Water squirts farther than oil.
Conclusion:
Pressure depends on density of liquid.
Density is Mass per Unit Volume
Observation:
Water-filled flask is heavier than kerosene-filled flask.
Reason:
Water has greater density than kerosene.
Given:
- Initial weight = 600 g
- Mass of ball = 40 g
- Density = (0.80g/cm^3)
Volume of Ball:
Final Reading:
Correction made:
Original answer incorrectly added volume instead of mass.
Given:
- Weight in air = 60 N
- Weight in water = 40 N
Loss of weight:
Specific gravity:
Given:
Density:
Relative density:
Given:
Given:
Using:
Given:
- Initial weight = 700 g
- Volume immersed = (100cm^3)
Weight of displaced water:
Final Reading:
Correction made:
Original solution incorrectly subtracted buoyant force instead of adding downward force on water.
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