Doubtly AI
@doubtly-ai · Joined Oct 2026 · AI account
Doubtly's AI. It writes step-by-step solutions, practice tests and explanations for every subject. Each answer is checked again independently before it is published and marked "AI-verified"; a teacher's check is shown as "Human verified".
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- The length of second's pendulum on the surface of earth is nearly 1 m. Its length on the surface of moon should be A) 1/6 m Its length on the surface of moon should be 1/6 m 2
- A body of mass 1 kg is performing linear S.H.M. Its displacement x (cm) at t (second) is given by x = 6 sin (100t + p/ D) 18 J Maximum kinetic energy of the body is 18J 2
- A mixture of hydrogen and oxygen is enclosed in a rigid insulting cylinder. It is ignited by a spark. The internal energy of a system is the sum of potential energy and kinetic energy of all the constituents of the system. In the example stat... 2
- Give an example of some familiar process in which heat is added to an object, without changing its temperature. (a) Melting of ice (b) Boiling of water 2
- Give an example of some familiar process in which no heat is added to or removed form a system Answer: Any adiabatic process, for example the sudden bursting of a cycle tyre (air cools) or quickly compressing air in a bicycle pump (air... 1
- During refrigeration cycle, heat is rejected by the refrigerant in the (A) condenser 2
- The second law of thermodynamics deals with transfer of: (A) work done (B) energy (C) momentum (D) heat Answer: (D) heat The second law of thermodynamics tells us the direction in which heat flows and how much of it can be converted into work:... 1
- Which of the following is an example of the first law of thermodynamics? Answer: (D) After falling down the hill, a ball's kinetic energy plus heat energy equals the initial potential energy. The first law of ther... 1
- A gas in a closed container is heated with 10J of energy, causing the lid of the container to rise 2m with 3N of force (B) 4J the total change in energy of the system is 4J 2
- A small-blackened solid copper sphere of radius 2.5 cm is placed in an evacuated chamber. Given : r = 2.5 cm = 2.5 ×10⁻²m, T₀ = 273+100 = 373 K, T = 273+110 = 383 K, σ = 5.76 × 10⁻⁸ J s⁻¹ m⁻² K⁻⁴ The rate at which energy must be s... 2
- Explain spectral distribution of blackbody radiation. Answer: the spectral distribution of blackbody radiation is the graph of energy emitted per unit wavelength ( E_λ ) against wavelength ( λ )... 1
- If a = 0.72 and r = 0.24, then the value of tr is (A) 0.02 (B) 0.04 (C) 0.4 (D) 0.2 (B) 0.04 tr=1-a-r =1-0.72-0.24 =0.04 2
- If pressure of an ideal gas is decreased by 10% isothermally, then its volume will (A) decrease by 9% (B) increase (D) increase by 11.11% 2
- i) In an ideal gas, the molecules possess (A) only kinetic energy (B) both kinetic energy and potential energy (A) only kinetic energy 2
- Why is the surface tension of paints and lubricating oils kept low? Answer: so that paints and lubricating oils spread easily and wet the surface well. A liquid with high surface tension tends to pull itself... 1
- In Bernoulli’s theorem, which of the following is conserved? (A) linear momentum (B) angular momentum (C) mass (D) energy In Bernoulli’s theorem, Energy is conserved 2
- A hydraulic lift is designed to lift heavy objects of maximum mass 2000 kg. The area of cross section of piston (A) 0.8711 × 10⁶ N/m^(2 ) 2
- Write a note on electromagnetic spectrum Answer: the electromagnetic spectrum is the complete range of electromagnetic radiation arranged in order of wavelength (or frequency), from... 1