11th
In this category students supposed to ask questions which belong to std 11th maharashtra board Science
- A planet has the same mean density as the earth but twice its radius. If the escape speed on earth is 11.2 km/s, the escape speed on the planet is Answer: A. 22.4 km/s v_e=√(2GM/R)=R√(8π Gρ/3)∝ R for equal density, so 2×11.2=22.4 km/s. 1
- At what height above the earth's surface does the acceleration due to gravity become one-fourth of its value on the surface? (R = 6400 km) Answer: A. 6400 km g/4=g/(1+h/R)²⇒1+h/R=2⇒ h=R . 1
- Blocks of mass 2 kg and 3 kg are in contact on a frictionless horizontal surface. A horizontal force of 10 N is applied to the 2 kg block. The contact force between the blocks is Answer: C. 6 N a=10/5=2 m/s²; force on 3 kg block =3×2=6 N. 1
- A ball of mass 0.15 kg moving at 20 m/s is hit straight back with the same speed. If the contact lasts 0.01 s, the average force on the ball is Answer: C. 600 N Δ p=0.15×40=6 N s; F=6/0.01=600 N. 1
- A projectile is fired so that its horizontal range equals its maximum height. The angle of projection with the horizontal is Answer: C. tan⁻¹(4) 2u²sinθcosθ/g=u²sin²θ/2g⇒tanθ=4 . 1
- A convex lens of focal length 20 cm is placed in contact with a concave lens of focal length 40 cm. The combination behaves as a Answer: D. convex lens of focal length 40 cm 1/F=frac120-frac140=frac140 ; positive, so converging, F = 40 cm. 1
- The critical angle for light going from glass (\(\mu=1.5\)) to air is Answer: B. sin⁻¹(2/3) sin C=frac1μ=2/3 . 1
- A source of frequency 900 Hz moves towards a stationary observer at 34 m/s. If the speed of sound is 340 m/s, the frequency heard is Answer: A. 1000 Hz n'=nv/v-v_s=900×340/306=1000 Hz. 1
- 100 g of water at 80 °C is mixed with 200 g of water at 20 °C. Neglecting heat losses, the final temperature is Answer: D. 40 °C 100(80-T)=200(T-20)⇒ T=40 °C. 1
- Explain how pressure of a dry gas can be calculated using aqueous tension. i. When a gas is collected over water in a closed container, it gets mixed with the saturated water vapour in that space. Therefore, the mea... 1
- A gas at 772 mm Hg and at 35 °C occupies a volume of 6.851 L. Calculate its volume at STP. Given: V₁ = Initial volume = 6.851 L P₁ = Initial pressure = 772 mm Hg, P₂ = Final pressure = 760 mm Hg T₁ = Initial temperature = 35 °C = 3... 1
- Find the temperature in °C at which volume and pressure of 1 mol of nitrogen gas becomes 10 dm3 and 2.46 P = 2.46 atm, V = 10 dm³, n = 1 mol, R = 0.0821 dm³-atm K⁻¹ mol⁻¹ To find: Temperature (T) Formula: PV = nRT According to ideal gas equation... 1
- Calculate the temperature of 5.0 mol of a gas occupying 5 dm3 at 3.32 bar. (R = 0.083 bar dm3 K-1 mol-1) Given: n = number of moles = 5.0 mol, V = volume = 5 dm³ P = pressure = 3.32 bar, R = 0.083 bar dm³ K⁻¹ mol⁻¹ To find: Temperature (T) Formu... 1
- Calculate the number of moles of hydrogen gas present in a 0.5 dm3 sample of hydrogen gas at a pressure Given: V = 0.5 dm³ = 0.5 × 10⁻³ m³, P = 101.325 kPa = 101.325 × 10³ Pa = 101.325 × 10³ Nm⁻² T = 27 °C = 27 + 273.15 K = 300.15 K, R = 8.314... 1
- What is an ideal gas? The gases which obey’ ideal gas equation over a complete range of temperature and pressure are called ideal gases. For an ideal gas, the rat... 1
- What are real gases? Gases, which do not obey ideal gas equation under all the conditions of temperature and pressure are called real gases. For real gases, the... 1
- Explain the reason for deviations of gases from ideal behaviour. A deviation from the ideal behaviour is observed at high pressure and low temperature. It is due to two reasons. The intermolecular attracti... 1
- Explain: Liquefaction of CO2 with the help of pressure vs volume isotherm. Answer: Andrews' P–V isotherms of CO₂ show that CO₂ can be liquefied by pressure only below its critical temperature, 30.98 °C; at this temp... 1
- Define: Critical temperature, critical volume and critical pressure. i. The temperature above which a substance cannot be liquified by increasing pressure is called its critical temperature (T_c). ii. The mola... 1
- Water has Tc = 647.1 K and Pc = 220.6 bar. What do these values imply about the state of water under ordinary conditions The T_c and P_c values of water are very high compared to the room temperature and common atmospheric pressure. As a result, water exists in... 1
- Gases possess characteristic critical temperature which depends upon the magnitude of intermolecular forces When cooling of ammonia and carbon dioxide gas is started from 500 K, then ammonia reaches its critical temperature first (i.e., 405.5 K.) a... 1
- CO2 has Tc = 38.98 °C and Pc = 73 atm. How many phases of CO2 coexist at i. 50 °C and 73 atm ii. 20 °C and 50 atm. i. 50 °C and 73 atm represent a condition for CO₂ above its T_c. Therefore, under this condition CO₂ exists only as single phase. ii. 20° C... 1
- In which of the following cases, water will have the highest and the lowest boiling point? Higher the pressure to which a liquid is exposed, higher will be its boiling point. The pressure to which water is exposed is maximum in the... 1
- Define: Liquid state Liquid state is the intermediate state between solid state and gaseous state. 2