Find and write down structures of 10 interesting small molecular weight
[question] Question. Find and write down structures of 10 interesting small molecular weight biomolecules. Find if there is any industry which manufactures the compounds by isolation. Find out who are the buyers [/question] [solution] Solution: [/solution]...
Read More →Nitrogen laser produces a radiation at a wavelength of 337.1 nm.
[question] Question. Nitrogen laser produces a radiation at a wavelength of $337.1 \mathrm{~nm}$. If the number of photons emitted is $5.6 \times 10^{24}$, calculate the power of this laser. [/question] [solution] Solution: Power of laser = Energy with which it emits photons Power $=E=\frac{\text { Nhe }}{\lambda}$ Where, N = number of photons emitted h = Planck’s constant c = velocity of radiation $\lambda=$ wavelength of radiation Substituting the values in the given expression of Energy (E): ...
Read More →Arrange the following type of radiations in increasing order of frequency:
[question] Question. Arrange the following type of radiations in increasing order of frequency: (a) radiation from microwave oven (b) amber light from traffic signal (c) radiation from FM radio (d) cosmic rays from outer space and (e) X-rays [/question] [solution] Solution: The increasing order of frequency is as follows: Radiation from FM radio < amber light < radiation from microwave oven < X- rays < cosmic rays The increasing order of wavelength is as follows: Cosmic rays < X-rays < radiation...
Read More →What is meant by tertiary structure of proteins?
[question] Question. What is meant by tertiary structure of proteins? [/question] [solution] Solution: The helical polypeptide chain undergoes coiling and folding to form a complex three-dimensional shape referred to as tertiary structure of proteins. These coils and folds are arranged to hide the non-polar amino acid chains and to expose the polar side chains. The tertiary structure is held together by the weak bonds formed between various parts of the polypeptide chain. [/solution]...
Read More →In fig, find tan P – cot R.
[question] Question. In fig, find tan P – cot R. [/question] [solution] Solution: In figure, by the Pythagoras Theorem $\mathrm{QR}^{2}=\mathrm{PR}^{2}-\mathrm{PQ}^{2}=(13)^{2}-(12)^{2}=25$ $\Rightarrow \mathrm{QR}=\sqrt{25}=5 \mathrm{~cm}$ In $\triangle \mathrm{PQR}$ right angled at $\mathrm{Q}, \mathrm{QR}=5 \mathrm{~cm}$ is side opposite to the angle $\mathrm{P}$ and $\mathrm{PQ}=12 \mathrm{~cm}$ is side adjacent to the angle P. Therefore, $\tan \mathrm{P}=\frac{\mathbf{Q R}}{\mathbf{P Q}}=\f...
Read More →Illustrate a glycosidic, peptide and a phospho-diester bond.
[question] Question. Illustrate a glycosidic, peptide and a phospho-diester bond. [/question] [solution] Solution: [/solution]...
Read More →An ion with mass number 56 contains 3 units of positive charge
[question] Question. An ion with mass number 56 contains 3 units of positive charge and 30.4% more neutrons than electrons. Assign the symbol to this ion. [/question] [solution] Solution: Let the number of electrons present in ion $\mathrm{A}^{3+}$ be $x$. $\therefore$ Number of neutrons in it $=x+30.4 \%$ of $x=1.304 x$ Since the ion is tripositive, $\Rightarrow$ Number of electrons in neutral atom $=x+3$ $\therefore$ Number of protons in neutral atom $=x+3$ Given, Mass number of the ion $=56$ ...
Read More →In $\triangle \mathrm{ABC}$, right angled at $\mathrm{B}, \mathrm{AB}=24 \mathrm{~cm}$,$B C=7 \mathrm{~cm}$. Determine :
[question] Question. In $\triangle \mathrm{ABC}$, right angled at $\mathrm{B}, \mathrm{AB}=24 \mathrm{~cm}$,$B C=7 \mathrm{~cm}$. Determine : (i) $\sin A, \cos A$ (ii) $\sin C, \cos C$. [/question] [solution] Solution: By Pythagoras Theorem, $\mathrm{AC}^{2}=\mathrm{AB}^{2}+\mathrm{BC}^{2}=(24)^{2}+(7)^{2}=625$ $\Rightarrow \mathrm{AC}=\sqrt{625}=25 \mathrm{~cm}$ (i) $\sin \mathrm{A}=\frac{\mathbf{B C}}{\mathbf{A C}}\left\{\right.$ ie, $\left.\frac{\text { sile opposite to ang } \mathbf{A}}{\tex...
Read More →What are macromolecules? Give examples.
[question] Question. What are macromolecules? Give examples. [/question] [solution] Solution: Macromolecules are large complex molecules that occur in colloidal state in intercellular fluid. They are formed by the polymerization of low molecular weight micromolecules. Polysaccharides, proteins, and nucleic acids are common examples of macromolecules. [/solution]...
Read More →A median of a triangle divides it into two triangles of equal areas
[question] Question. A median of a triangle divides it into two triangles of equal areas. Verify this result for ABC whose vertices are A(4, – 6), B(3,–2) and C(5,2) [/question] [solution] Solution: Here, the vertices of the triangles are A(4, –6), B(3, –2) and C(5, 2). Let D be the midpoint of BC. $\therefore \quad$ The coordinates of the mid point D are $\therefore \quad$ The coordinates of the mid point $D$ are $\left\{\frac{\mathbf{3}+\mathbf{5}}{\mathbf{2}}, \frac{-\mathbf{2}+\mathbf{2}}{\...
Read More →An ion with mass number 37 possesses one unit of negative charge.
[question] Question. An ion with mass number 37 possesses one unit of negative charge. If the ion contains 11.1% more neutrons than the electrons, find the symbol of the ion. [/question] [solution] Solution: Let the number of electrons in the ion carrying a negative charge be x. Then, Number of neutrons present $=x+11.1 \%$ of $x$ $=x+0.111 x$ $=1.111 x$ Number of electrons in the neutral atom $=(x-1)$ (When an ion carries a negative charge, it carries an extra electron) $\therefore$ Number of p...
Read More →A body is moving unidirectionally under the influence of a source
[question] Question. A body is moving unidirectionally under the influence of a source of constant power. Its displacement in time t is proportional to (i) $t^{\frac{1}{2}}$ (ii) $t$ (iii) $t^{\frac{3}{2}}$ (iv) $t^{2}$ [/question] [solution] solution: (iii) $t^{\frac{3}{2}}$ Power is given by the relation: P = Fv $=m a v=m v \frac{d v}{d t}=$ Constant $($ say,$k)$ $\therefore v d v=\frac{k}{m} d t$ $m$ Integrating both sides: $\frac{v^{2}}{2}=\frac{k}{m} t$ For displacement $x$ of the body, we ...
Read More →What is a centromere?
[question] Question. What is a centromere? How does the position of centromere form the basis of classification of chromosomes. Support your answer with a diagram showing the position of centromere on different types of chromosomes. [/question] [solution] Solution: Centromere is a constriction present on the chromosomes where the chromatids are held together. Chromosomes are divided into four types based on the position of the centromere. (i) Metacentric chromosome The chromosomes in which the c...
Read More →An element with mass number 81 contains 31.7% more neutrons as compared to protons.
[question] Question. An element with mass number 81 contains 31.7% more neutrons as compared to protons. Assign the atomic symbol. [/question] [solution] Solution: Let the number of protons in the element be $x$. Number of neutrons in the element $=x+31.7 \%$ of $x$ $=x+0.317 x$ $=1.317 x$ According to the question, Mass number of the element = 81 $\therefore$ (Number of protons $+$ number of neutrons $)=81$ $\Rightarrow x+1.317 x=81$ $2.317 x=81$ $x=\frac{81}{2.317}$ $=34.95$ $\therefore x=35$ ...
Read More →Find the area of the quadrilateral whose vertices taken in order are
[question] Question. Find the area of the quadrilateral whose vertices taken in order are (–4, –2), (–3, –5), (3, –2) and (2, 3). [/question] [solution] Solution: Join A and C. The given points are $\mathrm{A}(-4,-2), \mathrm{B}(-3,-5), \mathrm{C}(3,-2)$ and $\mathrm{D}(2,3)$ Area of $\triangle \mathrm{ABC}$ $=\frac{\mathbf{1}}{\mathbf{2}}[(-4)(-5+2)-3(-2+2)+3(-2+5)]$ $=\frac{\mathbf{1}}{\mathbf{2}}[12+0+9]=\frac{\mathbf{2 1}}{\mathbf{2}}=10.5$ sq. units Area of $\Delta \mathrm{ACD}$ $=\frac{1}{...
Read More →A body is initially at rest. It undergoes one-dimensional motion with
[question] Question. A body is initially at rest. It undergoes one-dimensional motion with constant acceleration. The power delivered to it at time t is proportional to (i) $t^{\frac{1}{2}}$ (ii) $t$ (iii) $t^{\frac{3}{2}}$ (iv) $t^{2}$ [/question] [solution] solution: Answer: (ii) t Mass of the body = m Acceleration of the body = a Using Newton’s second law of motion, the force experienced by the body is given by the equation: F = ma Both m and a are constants. Hence, force F will also be a con...
Read More →Find the area of the triangle formed by joining
[question] Question. Find the area of the triangle formed by joining the mid-points of the sides of the triangle whose vertices are (0, – 1), (2, 1) and (0, 3). Find the ratio of this area of the area of the given triangle. [/question] [solution] Solution: Let the vertices of the triangle be A(0, –1), B(2, 1) and C(0, 3). Let D, E and F be the mid-points of the sides BC, CA and AB respectively. Then : Coordinates of D are $\left(\frac{\mathbf{2}+\mathbf{0}}{\mathbf{2}}, \frac{\mathbf{1}+\mathbf{...
Read More →Answer carefully, with reasons:
[question] Question. Answer carefully, with reasons: (a) In an elastic collision of two billiard balls, is the total kinetic energy conserved during the short time of collision of the balls (i.e. when they are in contact)? (b) Is the total linear momentum conserved during the short time of an elastic collision of two balls? (c) What are the answers to (a) and (b) for an inelastic collision? (d) If the potential energy of two billiard balls depends only on the separation distance between their ce...
Read More →Symbols ${ }_{35}^{79} \mathrm{Br}$ and ${ }^{79} \mathrm{Br}$ can be written
[question] Question. Symbols ${ }_{35}^{79} \mathrm{Br}$ and ${ }^{79} \mathrm{Br}$ can be written, whereas symbols ${ }_{79}^{35} \mathrm{Br}$ and ${ }^{35} \mathrm{Br}$ are not acceptable. Answer briefly. [/question] [solution] Solution: The general convention of representing an element along with its atomic mass $(A)$ and atomic number $(Z)$ is ${ }_{Z}^{A} \mathrm{X}$. Hence, ${ }_{15}^{79} \mathrm{Br}$ is acceptable but is ${ }_{79}^{35} \ mathrm {Br}$ not acceptable. ${ }^{79} \mathrm{Br}$...
Read More →Describe the structure of the following with the help of labelled diagrams.
[question] Question. Describe the structure of the following with the help of labelled diagrams. (i) Nucleus (ii) Centrosome [/question] [solution] Solution: (i) Nucleus Nucleus controls all the cellular activities of the cell. It is spherical in shape. It is composed of the following structures: Nuclear membrane: It is a double membrane separating the contents of the nucleus from the cytoplasm. The narrow space between the two membranes is called the perinuclear space. Nuclear membrane has tiny...
Read More →State if each of the following statements is true or false. Give reasons for your answer.
[question] Question. State if each of the following statements is true or false. Give reasons for your answer. (a) In an elastic collision of two bodies, the momentum and energy of each body is conserved. (b) Total energy of a system is always conserved, no matter what internal and external forces on the body are present. (c) Work done in the motion of a body over a closed loop is zero for every force in nature. (d) In an inelastic collision, the final kinetic energy is always less than the init...
Read More →In each of the following find the value of 'k',
[question] Question. In each of the following find the value of 'k', for which the points are collinear. (i) (7, – 2), (5, 1), (3, k) (ii) (8,1), (k – 4), (2,–5). [/question] [solution] Solution: The given three points will be collinear if the $\Delta$ formed by them has equal to zero area. (i) Let $\mathrm{A}(7,-2), \mathrm{B}(5,1)$ and $\mathrm{C}(3, \mathrm{k})$ be the vertices of a triangle. $\therefore$ The given points will be collinear, if $\operatorname{ar}(\Delta \mathrm{ABC})=0$ or $7(...
Read More →Underline the correct alternative:
[question] Question. Underline the correct alternative: (a) When a conservative force does positive work on a body, the potential energy of the body increases/decreases/remains unaltered. (b) Work done by a body against friction always results in a loss of its kinetic/potential energy. (c) The rate of change of total momentum of a many-particle system is proportional to the external force/sum of the internal forces on the system. (d) In an inelastic collision of two bodies, the quantities which ...
Read More →Find the area of the triangle whose vertices are :
[question] Question. Find the area of the triangle whose vertices are : (i) (2,3), (–1, 0), (2, –4) (ii) (– 5, – 1), (3,–5), (5,2) [/question] [solution] Solution: (i) Let the vertices of the triangles be A(2, 3), B (–1, 0) and C(2, –4) Here $x_{1}=2, y_{1}=3$ $x_{2}=-1, y_{2}=0$ $x_{3}=2, y_{3}=-4$ $\because \quad$ Area of a $\Delta$ $=\frac{1}{\boldsymbol{2}}\left[\mathrm{x}_{1}\left(\mathrm{y}_{2}-\mathrm{y}_{3}\right)+\mathrm{x}_{2}\left(\mathrm{y}_{3}-\mathrm{y}_{1}\right)+\mathrm{x}_{3}\le...
Read More →Answer the following:
[question] Question. (a) The casing of a rocket in flight burns up due to friction. At whose expense is the heat energy required for burning obtained? The rocket or the atmosphere? (b) Comets move around the sun in highly elliptical orbits. The gravitational force on the comet due to the sun is not normal to the comet’s velocity in general. Yet the work done by the gravitational force over every complete orbit of the comet is zero. Why? (c) An artificial satellite orbiting the earth in very thin...
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