The distance moved by a particle travelling in straight line
Question: The distance moved by a particle travelling in straight line in $t$ seconds is given by $s=45 t+11 t^{2}-t^{3}$. The time taken by the particle to come to rest is Solution: (a) $9 \mathrm{sec}$ $s=45 t+11 t^{2}-t^{3}$ $\Rightarrow \frac{d s}{d t}=45+22 t-3 t^{2}$ According to the question, $3 t^{2}-22 t-45=0$ $\Rightarrow 3 t^{2}-27 t+5 t-45=0$ $\Rightarrow 3 t(t-9)+5(t-9)=0$ $\Rightarrow(t-9)(3 t+5)=0$ $\Rightarrow(t-9)=0$ or $(3 t+5)=0$ As time can't be negative, $t=9 \mathrm{sec}$...
Read More →The disease caused by a protozoan
Question: The disease caused by a protozoan and spread by an insect is (a) dengue (b) malaria (c) polio (d) measles Solution: (b) Malaria is the disease which is caused by the spread of a protozoan, i.e. Plasmodium. It is spread in healthy individuals by the bite of a female Anopheles mosquito carrying this Plasmodium in their mouth (saliva)....
Read More →The gas released during the preparation
Question: The gas released during the preparation of bread is (a) oxygen (b) carbon dioxide (c) nitrogen (d) sulphur dioxide Solution: (b) Carbon dioxide (CO2) is released during the preparation of bread. This is the process of fermentation in which yeast cells rapidly produces CO2, which causes risening of the dough used in preparation of bread....
Read More →The two micro organisms which live in symbiotic
Question: The two micro organisms which live in symbiotic association in lichens are (a) fungus and protozoa (b) alga and bacteria (c) bacteria and protozoa (d) alga and fungus Solution: (d) Lichens is an association between a fungal and an algal species. It is mutually benefiting association where algae provides food to the tongue fungus return gets shelter from it....
Read More →Pathogenic micro organisms present
Question: Pathogenic micro organisms present in host cells are killed by medicines called (a) pain killer (b) antibodies (c) antibiotics (d) vaccines Solution: (c) Antibiotics are substances that may inhibit or kill the growth of different microbes. Micro organisms causing infection in host bodies are killed by consumption of these antibiotics....
Read More →If a, b, c are in AP and x, y, z are in GP then prove that the value of
Question: If $a, b, c$ are in $A P$ and $x, y, z$ are in GP then prove that the value of $x^{b-c} \cdot y^{c-a}$. $z^{a-b}$ is 1 Solution: To prove: $x^{b-c} \cdot y^{c-a} \cdot z^{a-b}=1 \ldots$ (i) It is given that a,b,c are in A.P. $\Rightarrow 2 b=a+c \ldots$ (ii) And $x, y, z$, are in G.P. $\Rightarrow y^{2}=x z$ $\Rightarrow x=y^{2} / z$ Substitute this value of x in equation (i),we get L.H.S = $\Rightarrow\left(\frac{\mathrm{y}^{2}}{\mathrm{z}}\right)^{\mathrm{b}-\mathrm{c}} \times \mathr...
Read More →A disease in human beings
Question: A disease in human beings caused by virus is (a) typhoid (b) influenza (c) dysentery (d) cholera Solution: (b) Influenza is an infectious disease caused by the influenza virus. It is also known as flu whose symptoms includes high fever, running nose, sore throat, headache, coughing and muscle pain etc. Typhoid, dysentry and cholera are bacterial infections....
Read More →Which of the following reproduces
Question: Which of the following reproduces only inside a host cell? (a) Bacteria (b) Virus (c) Amoeba (d) Fungus Solution: (b) Virus is a micro organism, which is in an inactive or deal form outside the body of a host. It reproduces or replicates only when it enters a host and reaches its cells....
Read More →The volume of a sphere is increasing
Question: The volume of a sphere is increasing at $3 \mathrm{~cm}^{3} / \mathrm{sec}$. The rate at which the radius increases when radius is $2 \mathrm{~cm}$, is (a) $\frac{3}{32 \pi} \mathrm{cm} / \mathrm{sec}$ (b) $\frac{3}{16 \pi} \mathrm{cm} / \mathrm{sec}$ (c) $\frac{3}{48 \pi} \mathrm{cm} / \mathrm{sec}$ (d) $\frac{1}{24 \pi} \mathrm{cm} / \mathrm{sec}$ Solution: (b) $\frac{3}{16 \pi} \mathrm{cm} / \mathrm{sec}$ Let $r$ be the radius and $V$ be the volume of the sphere at any time $t$. The...
Read More →Solve this
Question: If $a, b, c$ are in GP and $a^{1 / x}=b^{1 / y}=c^{1 / z}$ then prove that $x, y, z$ are in AP. Solution: It is given that $a^{1 / x}=b^{1 / y}=c^{1 / z}$ Let $a^{1 / x}=b^{1 / y}=c^{1 / z}=k$ $\Rightarrow a^{1 / x}=k$ $\Rightarrow\left(a^{1 / x}\right)^{x}=k^{x} \ldots($ Taking power of $x$ on both sides. $)$ $\Rightarrow a^{1 / x \times x}=k^{x}$ $\Rightarrow a=k^{x}$ Similarly $b=k^{y}$ And $c=k^{z}$ It is given that a,b,c are in G.P. $\Rightarrow \mathrm{b}^{2}=\mathrm{ac}$ Substit...
Read More →Terms related to agricultural practices are given below.
Question: Terms related to agricultural practices are given below. Rearrange them in the correct sequence, harvesting, sowing, manuring, tilling and ploughing, irrigation, weeding. Solution: The correct sequence in the series of agricultural practices is: Tilling and ploughing Sowing Manuring Irrigation Weeding Havesting Tilling and ploughing It is the turning and loosening of soil to encourage growth of earthworms and microbes. It is the first step in preparation of soil. Sowing After soil prep...
Read More →The radius of a sphere is increasing at the rate of 0.2 cm/sec.
Question: The radius of a sphere is increasing at the rate of 0.2 cm/sec. The rate at which the volume of the sphere increase when radius is 15 cm, is (a) $12 \pi \mathrm{cm}^{3} / \mathrm{sec}$ (b) $180 \pi \mathrm{cm}^{3} / \mathrm{sec}$ (c) $225 \pi \mathrm{cm}^{3} / \mathrm{sec}$ (d) $3 \pi \mathrm{cm}^{3} / \mathrm{sec}$ Solution: (b) $180 \pi \mathrm{cm}^{3} / \mathrm{sec}$ Let $r$ be the radius and $V$ be the volume of the sphere at any time $t .$ Then, $\mathrm{V}=\frac{4}{3} \pi r^{3}$ ...
Read More →For discussion Despite being one of the growing economies,
Question: For discussion Despite being one of the growing economies, our country still has a large section of population going hungry and malnourished. Do you think an efficient crop production mechanism is the only solution to this? Discuss in the class what else needs to be done to root out hunger and malnutrition from our country. Solution: India, a growing economy with agriculture is a main contributor in its growth. Agriculture is science of cultivating plants, animals and other life forms ...
Read More →The radius of a sphere is increasing at the rate of 0.2 cm/sec.
Question: The radius of a sphere is increasing at the rate of 0.2 cm/sec. The rate at which the volume of the sphere increase when radius is 15 cm, is (a) $12 \pi \mathrm{cm}^{3} / \mathrm{sec}$ (b) $180 \pi \mathrm{cm}^{3} / \mathrm{sec}$ (c) $225 \pi \mathrm{cm}^{3} / \mathrm{sec}$ (d) $3 \pi \mathrm{cm}^{3} / \mathrm{sec}$ Solution: (b) $180 \pi \mathrm{cm}^{3} / \mathrm{sec}$ Let $r$ be the radius and $V$ be the volume of the sphere at any time $t .$ Then, $\mathrm{V}=\frac{4}{3} \pi r^{3}$ ...
Read More →Given below is a conversation between two farmers Heera and Beera.
Question: Given below is a conversation between two farmers Heera and Beera. Heera Brother Beera, your maize crops look beautiful. They have grown pretty fast. Beera Yes, I have sprayed urea this time. What about you? Heera Well, I am still relying on good old cow dung. I am saving money for buying a tractor.Beera Thats good. Tractor saves a Lot of time and labour. Heera Yes, its been very labour intensive for me and now these weeds have come up. Beera Try weedicides, they are very effective. No...
Read More →Write the quadratic equation, the arithmetic and geometric means of whose
Question: Write the quadratic equation, the arithmetic and geometric means of whose roots are A and G respectively. Solution: Let the roots of the required quadratic equation be a and b. The arithmetic and geometric means of roots are A and G respectively. $\Rightarrow A=(a+b) / 2 \ldots(i)$ And $\mathrm{G}=\sqrt{\mathrm{ab}}$ (ii) We know that the equation whose roots are given is = $x^{2}-(a+b) x+a b=0$ From (i) and (ii) we get: $\mathrm{x}^{2}-2 \mathrm{~A}+\mathrm{G}^{2}=0$ Thus, $x^{2}-2 A+...
Read More →Paddy is a major cereal crop in our country.
Question: Paddy is a major cereal crop in our country. (a) In which season is paddy cultivated? (b) Discuss the method of sowing. (c) What measures must be taken to prevent spoilage and insect attack of harvested grains? Solution: (a) Paddy is cultivated in rainy season as it is a kharif crop. (b) For sowing paddy, seeds are first grown in a nursery and later after selecting healthy seed plant lets, they are transplanted in the field. This allows us to select seedling which can survive in harshe...
Read More →The radius of the base of a cone is increasing at the rate of 3 cm/minute
Question: The radius of the base of a cone is increasing at the rate of 3 cm/minute and the altitude is decreasing at the rate of 4 cm/minute. The rate of change of lateral surface when the radius = 7 cm and altitude 24 cm is (a) $54 \pi \mathrm{cm}^{2} / \mathrm{min}$ (b) $7 \pi \mathrm{cm}^{2} / \mathrm{min}$ (c) $27 \mathrm{~cm}^{2} / \mathrm{min}$ (d) none of these Solution: Let $r$ be the radius, $h$ be the height and $S$ be the lateral surface area of the cone at any time $t .$ Given : $\f...
Read More →As a part of eco-club activity,
Question: As a part of eco-club activity, students were asked to raise a kitchen garden in the school premises. They were provided with some materials given in the box. List the other materials you would require. How will you plan the garden? Write the steps. Khurpi, water-can, spade, shovel Solution: Besides the given tools, the other items required for raising a garden are seeds and seedling of vegetables, plants from nursery, kitchen waste, manure, water, soil. Steps for raising the garden: K...
Read More →Despite favourable climatic conditions,
Question: Despite favourable climatic conditions, a farmers crop failed to give good yield. Give the possible reasons for this. Solution: If despite favourable climatic conditions, farmers crop failed to give good yield, the possibilities may be selection of crops was not done correctly. he did not use good quality and healthy seeds. his field was not well irrigated. manures/fertilisers were not timely and properly applied. weeds were not removed. seeds were not sown at appropriate distance. the...
Read More →If 2nd, 3rd and 6th terms of an AP are the three consecutive terms of a GP then
Question: If $2^{\text {nd }}, 3^{\text {rd }}$ and $6^{\text {th }}$ terms of an AP are the three consecutive terms of a GP then find the common ratio of the GP. Solution: We have been given that $2^{\text {nd }} 3^{\text {rd }}$ and $6^{\text {th }}$ terms of an $A P$ are the three consecutive terms of a GP. Let the three consecutive terms of the G.P. be a,ar,ar $^{2}$. Where $a$ is the first consecutive term and $r$ is the common ratio. $2^{\text {nd }}, 3^{\text {rd }}$ terms of the A.P. are...
Read More →(a) Name the practice followed for large scale
Question: (a) Name the practice followed for large scale rearing of farm animals. (b) What facilities are provided to farm animals? Solution: (a) The science of rearing, caring, breeding and improvement of domesticated animals is known as animal husbandry. It is the practice of breeding and raising livestock like cows, buffaloes, pigs, horses and sheep, etc. This practice requires good care and management of livestock. (b) The animals or livestock in animal husbandry practice should be provided ...
Read More →(a) Name the tool used with a tractor for
Question: (a) Name the tool used with a tractor for sowing seeds in a field. (b) What are the advantages of using this tool? Solution: (a) The tool used with a tractor for sowing seeds in a field at uniform distances is seed drill. Before the introduction of seed drill, the process was manual. (b) The advantages of seed drill are: Seeds are sown at a uniform distance and depth to avoid over crowding. After sowing, seeds are covered by soil which prevent them from being eaten by birds. It saves t...
Read More →What are organic
Question: What are organic foods? Solution: The crops that are cultivated using organic substances like manures, etc and prohibit the use of harmful chemical substances like fertilisers, pesticides, weedicides, etc., are called organic foods....
Read More →Beera wants to practice crop rotation in his field.
Question: Beera wants to practice crop rotation in his field. Suggest a rabi crop and a kharif crop which will replenish his field with nitrogen. Which crop replenishes nitrogen and why? Solution: Rabi crops are wheat, pea, mustard while kharif crops are maize, paddy (rice) or soyabean, These are grown in different seasons and therefore, can very well be rotated alternatively. Pea and soyabean are leguminous plants which harbour bacteria, i.e, Rhizobium in their nodules, thus help in fixing nitr...
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