eSaral - JEE | NEET | Class 8-10 Exam Prep App

What is the SI unit of mass? How is it defined?

[question] Question. What is the SI unit of mass? How is it defined? [/question] [solution] Solution: The SI unit of mass is kilogram (kg). 1 Kilogram is defined as the mass equal to the mass of the international prototype of kilogram [/solution]...

Which of the following are APs ?

[question] Question. Which of the following are APs ? If they form an AP, find the common difference d and write three more terms. (i) $2,4,8,16, \ldots$ (ii) $2, \frac{5}{2}, 3, \frac{7}{2}, \ldots$ (iii) $-1.2,-3.2,-5.2,-7.2, \ldots$ (iv) $-10,-6,-2,2, \ldots \ldots$ (v) $3,3+\sqrt{2}, 3+2 \sqrt{2}, 3+3 \sqrt{2}, \ldots$ (vi) $0.2,0.22,0.222,0.2222, \ldots .$ (vii) $\quad 0,-4,-8,-12, \ldots .$ (viii) $-\frac{1}{2},-\frac{1}{2},-\frac{1}{2},-\frac{1}{2}, \ldots$ (ix) $1,3,9,27, \ldots \ldots$ ...

State two economically important uses of:

[question] Question. State two economically important uses of: (a) Heterotrophic bacteria (b) Archaebacteria [question] [solution] Solution: (a) Heterotrophic bacteria (1) They act as decomposers and help in the formation of humus. (2) They help in the production of curd from milk. (3) Many antibiotics are obtained from some species of bacteria. (4) Many soil bacteria help in fixation of atmospheric nitrogen. (b) Archaebacteria (1) Methane gas is produced from the dung of ruminants by the methan...

Pressure is determined as force per unit area of the surface.

[question] Question. Pressure is determined as force per unit area of the surface. The SI unit of pressure, Pascal is as shown below $1 \mathrm{~Pa}=1 \mathrm{~N} \mathrm{~m}^{-2}$ If mass of air at sea level is $1034 \mathrm{~g} \mathrm{~cm}^{-2}$, calculate the pressure in Pascal. [/question] [solution] Solution: Pressure is defined as force acting per unit area of the surface. $=1.01332 \times 10^{5} \mathrm{~kg} \mathrm{~m}^{-1} \mathrm{~s}^{-2}$ We know $1 \mathrm{~N}=1 \mathrm{~kg} \mathrm...

Discuss how classification systems have undergone several changes over a period of time?

[question] Question. Discuss how classification systems have undergone several changes over a period of time? [/question] [solution] Solution: The classification systems have undergone several changes with time. The first attempt of classification was made by Aristotle. He classified plants as herbs, shrubs, and trees. Animals, on the other hand, were classified on the basis of presence or absence of red blood cells. This system of classification failed to classify all the known organisms. There...

If the density of methanol is $0.793 \mathrm{~kg} \mathrm{~L}^{-1}$,

[question] Question. If the density of methanol is $0.793 \mathrm{~kg} \mathrm{~L}^{-1}$, what is its volume needed for making $2.5 \mathrm{~L}$ of its 0.25 M solution? [/question] [solution] Solution: Molar mass of methanol $\left(\mathrm{CH}_{3} \mathrm{OH}\right)=(1 \times 12)+(4 \times 1)+(1 \times 16)$ $=32 \mathrm{~g} \mathrm{~mol}^{-1}$ $=0.032 \mathrm{~kg} \mathrm{~mol}^{-1}$ Molarity of methanol solution $=\frac{0.793 \mathrm{~kg} \mathrm{~L}^{-1}}{0.032 \mathrm{~kg} \mathrm{~mol}^{-1}}...

Illustrate the taxonomical hierarchy with suitable examples of a plant and an animal.

[question] Question. Illustrate the taxonomical hierarchy with suitable examples of a plant and an animal. [/question] [solution] Solution: The arrangement of various taxa in a hierarchical order is called taxonomic hierarchy. In this hierarchy, species is present at the lowest level whereas kingdom is present at the highest level. Classification of a plant As an example, let us classify Solanum melongena (Brinjal). Kingdom – Plantae Division – Angiospermae Class – Dicotyledonae Order – Solanale...

Explain clearly, with examples, the distinction between:

[question] Question. Explain clearly, with examples, the distinction between: (a) magnitude of displacement (sometimes called distance) over an interval of time, and the total length of path covered by a particle over the same interval; (b) magnitude of average velocity over an interval of time, and the average speed over the same interval. [Average speed of a particle over an interval of time is defined as the total path length divided by the time interval]. Show in both (a) and (b) that the se...

For the following APs,

[question] Question. For the following APs, write the first term and the common difference : (i) $3,1,-1,-3, \ldots$ (ii) $-5,-1,3,7, \ldots \ldots$ (iii) $\frac{1}{3}, \frac{5}{3}, \frac{9}{3}, \frac{13}{3}, \ldots$ (iv) $0.6,1.7,2.8,3.9, \ldots$ [/question] [solution] Solution: (i) $\mathrm{a}=3, \mathrm{~d}=\mathrm{t}_{2}-\mathrm{t}_{1}=1-3=-2$, i.e., $d=-2$ (ii) $a=-5, d=4$ (iii) $a=\frac{1}{3}$ $\mathrm{d}=\mathrm{t}_{2}-\mathrm{t}_{1}=\frac{5}{3}-\frac{1}{3}=\frac{4}{3}$ (iv) $0.6,1.7,2.8,...

A ball is dropped from a height of 90 m on a floor.

[question] Question. A ball is dropped from a height of $90 \mathrm{~m}$ on a floor. At each collision with the floor, the ball loses one tenth of its speed. Plot the speed-time graph of its motion between $t=0$ to $12 \mathrm{~s} .$ [/question] [solution] solution: Ball is dropped from a height, s = 90 m Initial velocity of the ball, $u=0$ Acceleration, $a=g=9.8 \mathrm{~m} / \mathrm{s}^{2}$ Final velocity of the ball $=v$ From second equation of motion, time $(t)$ taken by the ball to hit the ...

What is the concentration of sugar $\left(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\right)$ in $\mathrm{mol} \mathrm{L}^{-1}$ if its $20 \mathrm{~g}$ are dissolved in enough

[question] Question. What is the concentration of sugar $\left(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\right)$ in $\mathrm{mol} \mathrm{L}^{-1}$ if its $20 \mathrm{~g}$ are dissolved in enough water to make a final volume up to 2 L? [/question] [solution] Solution: Molarity (M) of a solution is given by $=0.02925 \mathrm{~mol} \mathrm{~L}^{-1}$ $\therefore$ Molar concentration of sugar $=0.02925 \mathrm{~mol} \mathrm{~L}^{-1}$ [/solution]...

Write first four terms of the AP,

[question] Question. Write first four terms of the AP, when the first term a and the common difference d are given as follows: (i) $a=10, d=10$ (ii) $a=-2 \quad d=0$ (iii) $\mathrm{a}=4, \mathrm{~d}=-3$ (iv) $\mathrm{a}=-1, \mathrm{~d}=1 / 2$ (v) $\mathrm{a}=-1.25, \quad \mathrm{~d}=-0.25$ [/question] [solution] Solution: (i) $\mathrm{t}_{1}=\mathrm{a}=10$, $t_{2}=10+d=10+10=20$ $t_{3}=20+d=20+10=30$ $\mathrm{t}_{4}=30+\mathrm{d}=30+10=40, \ldots .$ Thus, the AP is $10,20,30,40, \ldots$ (ii) Giv...

How is a key helpful in the identification

[question] Question. How is a key helpful in the identification and classification of an organism? [/question] [solution] Solution: Key is another taxonomical aid that helps in identification of plant and animal species. These keys are based on similarities and dissimilarities in characters, generally in a pair called couplet. Each statement in a taxonomic key is referred to as a lead. For categorizing each taxonomic rank, such as family, genus, species, etc., different keys are used. It is also...

In three moles of ethane $\left(\mathrm{C}_{2} \mathrm{H}_{6}\right)$, calculate the following:

[question] Question. In three moles of ethane $\left(\mathrm{C}_{2} \mathrm{H}_{6}\right)$, calculate the following: (i)Number of moles of carbon atoms. (ii)Number of moles of hydrogen atoms. (iii)Number of molecules of ethane [/question] [solution] Solution: (i) 1 mole of $\mathrm{C}_{2} \mathrm{H}_{6}$ contains 2 moles of carbon atoms. $\therefore$ Number of moles of carbon atoms in 3 moles of $\mathrm{C}_{2} \mathrm{H}_{6}$ = 2 × 3 = 6 (ii) 1 mole of $\mathrm{C}_{2} \mathrm{H}_{6}$ contains 6...

Define and understand the following terms:

[question] Question. Define and understand the following terms: (i) Phylum (ii) Class (iii) Family (iv) Order (v) Genus [/question] [solution] Solution: (i) Phylum Phylum is the primary division of kingdom. It includes one or more related classes of animals. In plants, instead of phylum, the term ‘division’ is used. (ii) Class Class is a taxonomic group consisting of one or more related orders. For example, the class, Mammalia, includes many orders. (iii) Family Family is a taxonomic group conta...

In which of the following situations,

[question] Question. In which of the following situations, does the list of numbers involved make an arithmetic progression, and why? (i) The taxi fare after each km when the fare is Rs. 15 for the first km and Rs. 8 for each additional km. (ii) The amount of air present in a cylinder when a vacuum pump removes 1/4 of the air remaining in the cylinder at a time. (iii) The cost of digging a well after every metre of digging, when it costs Rs. 150 for the first metre and rises by Rs. 50 for each s...

Read each statement below carefully and state with reasons and examples,

[question] Question. Read each statement below carefully and state with reasons and examples, if it is true or false; A particle in one-dimensional motion (a) with zero speed at an instant may have non-zero acceleration at that instant (b) with zero speed may have non-zero velocity, (c) with constant speed must have zero acceleration, (d) with positive value of acceleration mustbe speeding up. [/question] [solution] solution: Answer: (a) True (b) False (c) True (d) False Explanation: (a) When an...

Try to collect all the currently accepted meanings for the word ‘species’.

[question] Question. Try to collect all the currently accepted meanings for the word ‘species’. Discuss with your teacher the meaning of species in case of higher plants and animals on one hand and bacteria on the other hand. [/question] [solution] Solution: In biological terms, species is the basic taxonomical rank. It can be defined as a group of similar organisms that are capable of interbreeding under natural conditions to produce fertile offsprings. Therefore, a group of similar individuals...

Calculate the atomic mass (average) of chlorine using the following data

[question] Question. Calculate the atomic mass (average) of chlorine using the following data [/question] [solution] Solution: The average atomic mass of chlorine = 26.4959 + 8.9568 = 35.4527 u The average atomic mass of chlorine = 35.4527 u [/solution]...

A player throws a ball upwards with an initial speed of $29.4 \mathrm{~m} \mathrm{~s}^{-1}$.

[question] Question. A player throws a ball upwards with an initial speed of $29.4 \mathrm{~m} \mathrm{~s}^{-1}$. (a) What is the direction of acceleration during the upward motion of the ball? (b) What are the velocity and acceleration of the ball at the highest point of its motion? (c) Choose the $x=0 \mathrm{~m}$ and $t=0 \mathrm{~s}$ to be the location and time of the ball at its highest point, vertically downward direction to be the positive direction of $x$-axis, and give the signs of posi...

Determine the molecular formula of an oxide of iron in which the mass per cent of iron

[question] Question. Determine the molecular formula of an oxide of iron in which the mass per cent of iron and oxygen are $69.9$ and $30.1$ respectively. Given that the molar mass of the oxide is $159.69 \mathrm{~g} \mathrm{~mol}^{-1}$. [/question] [solution] Solution: Mass percent of iron (Fe) = 69.9% (Given) Mass percent of oxygen (O) = 30.1% (Given) Number of moles of iron present in the oxide $=\frac{69.90}{55.85}$ = 1.25 Number of moles of oxygen present in the oxide $=\frac{30.1}{16.0}$ =...

Can you identify the correct sequence of taxonomical categories?

[question] Question. Can you identify the correct sequence of taxonomical categories? (a) Species $\rightarrow$ Order $\rightarrow$ Phylum $\rightarrow$ Kingdom (b) Genus $\rightarrow$ Species $\rightarrow$ Order $\rightarrow$ Kingdom (c) Species $\rightarrow$ Genus $\rightarrow$ Order $\rightarrow$ Phylum [/question] [solution] Solution: The correct hierarchical arrangement of taxonomic categories in ascending order is Species $\rightarrow$ Genus $\rightarrow$ Family $\rightarrow$ Order $\right...

Is it possible to design a rectangular park of perimeter $80 \mathrm{~m}$ and area $400 \mathrm{~m}^{2}$ ?

[question] Question. Is it possible to design a rectangular park of perimeter $80 \mathrm{~m}$ and area $400 \mathrm{~m}^{2} ?$ If so, find its length and breadth. [/question] [solution] Solution: Perimeter of the rectangular park = 80 m $\Rightarrow$ Length $+$ Breath of the park $=\frac{\mathbf{8 0}}{\mathbf{2}} \mathrm{m}=40 \mathrm{~m}$. Let the breadth be x metres, then length = (40 – x) m Here, $x<40$ $x \times(40-x)=400[$ Each $=$ area of the park $]$ i.e., $-x^{2}+40 x-400=0$ i.e., $x^{2...

Is the following situation possible?

[question] Question. Is the following situation possible? If so, determine their present ages. The sum of the ages of two friends is 20 years. Four years ago, the product of their ages in year was 48. [/question] [solution] Solution: Let the age of one friend be x years. Age of the other friend will be (20 – x) years. 4 years ago, age of 1st friend = (x – 4) years And, age of 2nd friend = (20 – x – 4) $=(16-x)$ years Given that, $(x-4)(16-x)=48$ $16 x-64-x^{2}+4 x=48$ $-x^{2}+20 x-112=0$ $x^{2}-...

Is it possible to design a rectangular mango grove whose length is twice its breadth,

[question] Question. Is it possible to design a rectangular mango grove whose length is twice its breadth, and area is $800 \mathrm{~m}^{2}$ ? If so, find its length and breadth. [/question] [solution] Solution: Let x be the breadth and 2x be the length of the rectangle. $x \times 2 x=800$ $\Rightarrow 2 x^{2}=800$ $\Rightarrow x^{2}=400=(20)^{2}$ $\Rightarrow x=20$ Hence, the rectangle is possible and it has breadth $=20 \mathrm{~m}$ and length $=40 \mathrm{~m}$. [/solution]...

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