12th Science Maharashtra Board
In this category students supposed to ask questions which belong to std 12th maharashtra board Science
- Twenty seven droplets of water, each of radius 0.1 mm coalesce into a single drop. Find the change in surface energy. Surface tension of water is 0.072 N/m. Correct answer = 1.628 x 10⁻⁷ J Explaination :: Given :: r=0.1mm =0.1 x 10⁻³m , T=0.072 N/m Let R be the radius of the single drop formed du... 1
- An air bubble of radius 0.2 mm is situated just below the water surface. Calculate the gauge pressure. Surface tension of water = 7.2x 10-2 N/m. Correct Answer: 720 N/m² Explaination:: Given : Radius of bubble =0.2 mm = 2× 10⁻⁴ m , surface tension of water = 0.072 N/m = 720× 10⁻⁴ N/m... 1
- Calculate the rise of water inside a clean glass capillary tube of radius 0.1 mm, when immersed in water of surface tension 7x10-2 N/m. Correct Answer = 0.142 m Explaination Given:: r = 0.1 mm = 10⁻⁴ m, T = 7 × 10⁻² N/m, θ = 0°, ρ = 1000 kg/m³, g = 9.8 m/s^(2 ) To find: Heigh... 1
- The pressure of water inside the closed pipe is 3 x105 N/m2. This pressure reduces to 2x105 N/m2 on opening the value of the pipe. Correct answer = 14.14 m/s Explaination:: Given:: p₁ = 3 × 10⁵ Pa, v₁ = 0, p₂ = 2 × 10⁵ Pa, ρ = 10³ kg/m³ Assuming the potential head to be... 1
- With what velocity does water flow out of an orifice in a tank with gauge pressure 4 x105 N/m2 before the flow starts? Correct answer= 28.28 m/s Explaination Given:: p - p₀ = 4 × 10⁵ Pa, ρ = 10³ kg/m³ If the orifice is at a depth h from the water surface in a... 1
- The speed of water is 2m/s through a pipe of internal diameter 10 cm. Correct answer =7.07 x 10⁻² m Explaination:: Given : d1=10cm =0.1 m , v1=2m/s, v2=4m/s Solution: by the equation of continuity , the ratio o... 1
- With what terminal velocity will an air bubble 0.4 mm in diameter rise in a liquid of viscosity 0.1 Ns/m2 and Answer= - 0.782 × 10^(-3 )m/s (upwards) Given: d=0.4 mm, r=d/2 = 0.2mm= 2×10⁻⁴ m, , h = 0.1 Pa-s, p_L = 0.9 × 10³ kg/m^(3 )= 900 kg/m³, ^( )... 1
- A horizontal force of 1 N is required to move a metal plate of area 10-2 m2 with a velocity of Correct answer= 7.5 Ns/m² Explaination:: Given : F=1, A=10⁻² m^(2, )v_(0 )=2 × 10⁻² m/s, y=1.5 × 10⁻³ m Solution: Velocity gradient, dv/dy =... 1
- Calculate the viscous force acting on a rain drop of diameter 1 mm, falling with a uniform velocity 2 m/s through air. Correct answer = 3.394 ×10^(-7 )N or 3.393 ×10^(-7 )N Explaination:: Given: d= 1 mm, v_(0 )= 2 m/s, η= 1.8 × 10⁻⁵ Ns/m² r =d/2 =0.5 mm = 5 ×... 1
- In a hydraulic lift, the input piston had surface area 30 cm2 and the output piston has surface area of 1500 cm2. Correct answer = 1250 N Explaination:: Given : A_(1 )= 30 cm^(2 )= 3×10⁻³ m² , A₂ = 1500 cm^(2 )= 0.15 m^(2 )F₁=25 N By Pascal’s law F1/A1=F... 1
- Find the pressure 200 m below the surface of the ocean if pressure on the free surface of liquid is one atmosphere Correct Answer= 21.789×10^(5 )N/m² Explaination:: Given : h=200 m, ρ=1060 kg/m^(3 )p_(0 )= 1.013×10^(5 )Pa, g = 9.8 m/s² Absolute pressure,... 1
- Derive an expression for capillary rise for a liquid having a concave meniscus. Consider a capillary tube of radius r partially immersed into a wetting liquid of density p. Let the capillary rise be h and q be the angle... 1
- Explain the capillary action When a capillary tube is partially immersed in a wetting liquid, there is a capillary rise and the liquid meniscus inside the tube is concav... 1
- Obtain an expression for conservation of mass starting from the equation of continuity. Consider a fluid in steady or streamline flow, that is its density is constant. The velocity of the fluid within a flow tube, while everywhe... 1
- Derive an expression of excess pressure inside a liquid drop . Consider a spherical drop of radius R and surface tension T Let p_i be the pressure inside the drop and p₀ be the pressure outside it. As th... 1
- Why does the speed of a liquid increase and its pressure decrease when a liquid passes through constriction in a horizontal pipe? Consider a horizontal constricted tube. Let A_(1 )and A₂ be the cross-sectional areas at points P₁ and P₂, respectively. Let v₁ and v₂ be th... 1
- Why does velocity increase when water flowing in broader pipe enters a narrow pipe? When a tube narrows, the same volume occupies a greater length, as schematically shown in Fig. A₁ is the cross section of the broader pipe a... 1
- Why two or more mercury drops form a single drop when brought in contact with each other? A spherical shape has the minimum surface area-to-volume ratio of all geometric forms. When two drops of a liquid are brought in contact, th... 1
- What is an incompressible fluid? A fluid which does not undergo change in volume for a large range of pressures. Thus, its density remains constant throughout the fluid for... 1
- Why is a low density liquid used as a manometric liquid in a physics laboratory? An open tube manometer measures the gauge pressure, p = p0 + hρg, where p is the pressure being measured, p0 is the atmospheric pressure, h... 1
- What is the basis of the Bernoulli's principle? Conservation of energy is the basis of the Bernoulli’s principle Bernoulli’s equation states that the work done per unit volume of a fluid b... 1
- How much amount of work is done in forming a soap bubble of radius r? Let T be the surface tension of a soap solution. The initial surface area of soap bubble = 0 The final surface area of soap bubble = 2 × 4πr... 1
- Why is the surface tension of paints and lubricating oils kept low? For better wettability (surface coverage), the surface tension and angle of contact of paints and lubricating oil must be low. 1
- 1) Multiple Choice Questions chapter 2 Mechanical Properties of Fluids maharashtra board i) A hydraulic lift is designed to lift heavy objects of maximum mass 2000 kg. The area of cross section of piston carrying the load is 2.25... 1