1. A block of wood floats on water but sinks in alcohol. Which statement is correct?
A) Alcohol is denser than water
B) The buoyant force in alcohol is more
C) The density of block is less than water but more than alcohol
D) The pressure exerted by water is less than alcohol
2. A force of 300 N is applied on a surface of area 50 cm². What is the pressure?
A) 6x10 Pa
B) 6x10 Pa
C) 6×10⁰ Pa
D) 6x10 Pa
3. In vacuum, what will be the pressure inside it?
A) 760 mm of Hg
B) 1 Pa
C) 101 KPa
D) Zero
4. Why does liquid come out through the needle at high speed when the syringe is pressed?
A) Force is reduced
B) Force is increased and area is small
C) Pressure is reduced
D) Density of liquid changes
5. A dam is thicker at the bottom than at the top because
A) Water pressure decreases with depth
B) Water pressure increases with depth
C) The shape of dam looks good
D) It stores more water at the top
6. An object weighs 50 N in air and 30 N in water. What is the buoyant force acting on it?
A) 20 N
B) 80 N
C) 30 N
D) 50 N
7. In which condition will the greatest pressure be produced?
A) 100 N force on 2 m²
B) 200 N force on 4 m²
C) 400 N force on 5 m²
D) 300 N force on 3 m²
Answer (2)
The correct statement is C) The density of block is less than water but more than alcohol . When a block of wood floats on water, it means its density is less than that of water. If it sinks in alcohol, its density is more than that of alcohol. This means that the density of the block is between the densities of water and alcohol.
Pressure is calculated using the formula: Pressure = Area Force Given force = 300 N and area = 50 cm² = 0.005 m², the pressure is: Pressure = 0.005 m 2 300 N = 60000 Pa So, the correct option is B) 6 \times 10^4 \text{ Pa} .
In a vacuum, there is no matter to exert pressure. Therefore, the pressure inside a vacuum is D) Zero .
The reason liquid comes out through the needle at high speed when the syringe is pressed is B) Force is increased and area is small . According to Pascal's principle, when force is applied on a fluid, the pressure is transmitted equally. The small area of the needle increases the pressure, causing the liquid to emerge at high speed.
A dam is thicker at the bottom than at the top because B) Water pressure increases with depth . The deeper you go, the more water there is above exerting pressure, so the dam must be thicker to withstand this increased pressure.
The buoyant force acting on an object is equal to the difference in weight in air and in water, which is A) 20 N . Buoyant force = Weight in air − Weight in water = 50 N − 30 N = 20 N
The greatest pressure is produced where the force per unit area is largest. We calculate pressure for each option:
A) 2 m 2 100 N = 50 Pa
B) 4 m 2 200 N = 50 Pa
C) 5 m 2 400 N = 80 Pa
D) 3 m 2 300 N = 100 Pa So, the correct option is D) 300 N force on 3 m² .
The answers are as follows: 1) C, 2) B, 3) D, 4) B, 5) B, 6) A, 7) D. Each explanation relates to basic principles of physics such as buoyancy, pressure, and the behavior of fluids. Understanding these principles provides a foundation for further studies in physics.
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