Trees help in reducing the pollution of our environment.
Question: Trees help in reducing the pollution of our environment. Lakhs of trees are planted by people in the month of July every year. This occasion is called (a) Forest Conservation Day (b) Plantation month (c) Van Mahotsav (d) Wildlife week Solution: (c) Van Mahotsav is a occasion when lakhs of trees are planted in July every year....
Read More →A pond contains clean water.
Question: A pond contains clean water. Which of the following activities will produce least pollution of water? (a) Washing clothes in the pond (b) Bathing animals in the pond (c) Washing motor vehicles in the pond (d) Swimming in the pond Solution: (d) Swimming in the pond is the activity which will produces least pollution of water....
Read More →Which, of the following procedures
Question: Which, of the following procedures will give you water free from all impurities? (a) Adding chlorine tablets (b) Distillation (c) Boiling (d) Filtration Solution: (c) When water is heated, it boils at a temperature of 100C. At this high temperature, all the harmful microorganisms (or germs) present in water are killed and it becomes absolutely safe for drinking....
Read More →Potable water is the water which is
Question: Potable water is the water which is (a) obtained from a river (b) obtained from a lake (c) pure and fit for drinking (d) used only for washing clothes Solution: (c) Potable water is the water which is pure and fit for drinking. Water can be made potable by various methods such as boiling, etc....
Read More →The phenomenon of ‘warble cancer’
Question: The phenomenon of warble cancer is due to (a) soot particles (b) CFCs (c) log (d) acid rain Solution: (d) The phenomenon of marble cancer Is due to acid rain. Marble cancer is corrosion of buildings or monuments by acid rain....
Read More →Incomplete combustion of fuel such
Question: Incomplete combustion of fuel such as petrol and diesel gives (a) nitrogen oxide (b) sulphur dioxide (c) carbon monooxide (d) carbon dioxide Solution: (c) Carbon monoxide is produced by the incomplete combustion of fuels like wood, coal, kerosene, petrol and diesel....
Read More →The type of pollution which is likely
Question: The type of pollution which is likely to affect Taj Mahal in Agra to a greater extent is (a) air pollution (b) water pollution (c) soil pollution (d) noise pollution Solution: (a) The type of pollution which is likely to affect Taj Mahal in Agra to a greater extent is air pollution. It is affectingTaj Mahal by corroding it and yellowing its marble....
Read More →Which of the following is not a way
Question: Which of the following is not a way to conserve water? (a) Replace (b) Reduce (c) Reuse (d) Recycle Solution: (a) Replace is not a way to conserve water. At our individual level, we should consciously save water and not to waste it. Reduce, reuse and recycle should be our mantra....
Read More →Boojho wishes to contribute in reducing
Question: Boojho wishes to contribute in reducing air pollution. Which vehicle should he use for going to school? (a) Car (b) School bus (c) Autorickshaw (d) Scooter Solution: (b) Boojho, if wishes to contribute in reducing air pollution, should use school bus for going to school. A school bus carry many children together, thus vehicular emissions are reduced....
Read More →Which of the following is not a source
Question: Which of the following is not a source of air pollution? (a) Automobile exhaust (b) Burning of firewood (c) Windmill (d) Power plant Solution: (c) Windmill is not a source of air pollution. It is regarded as an alternative source of energy....
Read More →Air is a mixture of various gases.
Question: Air is a mixture of various gases. One of the gas is 21% part of the air and is essential for the survival of human beings. This gas is (a) nitrogen (b) oxygen (c) ozone (d) argon Solution: (b) Oxygen makes up about 21 % of air by volume. It is essential for the survival of human beings....
Read More →Solve this
Question: If $\cos x=\frac{-\sqrt{15}}{4}$ and $\frac{\pi}{2}x\pi$ find the value of sin x. Solution: Given: $\cos x=-\frac{\sqrt{15}}{4}$ To find: value of sinx Given that: $\frac{\pi}{2}x\pi$ So, x lies in IInd quadrant and sin will be positive. We know that, $\cos ^{2} \theta+\sin ^{2} \theta=1$ Putting the values, we get $\left(-\frac{\sqrt{15}}{4}\right)^{2}+\sin ^{2} \theta=1$ [Given] $\Rightarrow \frac{15}{16}+\sin ^{2} \theta=1$+ $\Rightarrow \sin ^{2} \theta=1-\frac{15}{16}$ $\Rightarro...
Read More →Solve this
Question: If $\sin x=-\frac{2 \sqrt{6}}{5}$and $x$ lies in Quadrant III, find the values of $\cos x$ and $\cot x$. Solution: Given: $\sin x=-\frac{2 \sqrt{6}}{5}$ To find: cos x and cot x Since, $x$ is in IIIrd Quadrant. So, sin and cos will be negative but tan will be positive. We know that, $\sin ^{2} x+\cos ^{2} x=1$ Putting the values, we get $\left(-\frac{2 \sqrt{6}}{5}\right)^{2}+\cos ^{2} x=1$ [Given] $\Rightarrow \frac{24}{25}+\cos ^{2} x=1$ $\Rightarrow \cos ^{2} x=1-\frac{24}{25}$ $\Ri...
Read More →Write the names of all planets in the figure.
Question: Write the names of all planets in the figure. Solution: According to orbits (starting from the first), the names of planets are : (i) Mercury (ii)Venus (iii)Earth (iv) Mars (v) Jupiter (vi) Saturn (vii)Uranus (viii) Neptune...
Read More →Solve this
Question: If $\sec \theta \sqrt{2}$ and $\theta$ lies in Quadrant IV, find the values of all the other five trigonometric functions. Solution: Given: $\sec \theta=\sqrt{2}$ Since, $\theta$ is in IV th Quadrant. So, sin and tan will be negative but $\cos$ will be positive. Now, we know that $\cos \theta=\frac{1}{\sec \theta}$ Putting the values, we get $\cos \theta=\frac{1}{\sqrt{2}}$ (i) We know that, $\cos ^{2} \theta+\sin ^{2} \theta=1$ Putting the values, we get $\left(\frac{1}{\sqrt{2}}\righ...
Read More →Explain why we always see
Question: Explain why we always see the same side of the moon. Solution: We always see the same side of the moon because the period of rotation of the moon on its axis is equal to the period of its revolution around the earth, so we only see the side that faces us and this side faces at us all the time,...
Read More →Suppose the moon emits light
Question: Suppose the moon emits light of its own. Would it still have phases? Justify your answer. Solution: No, it will not have the phases because the phases are due to the reflection of different intensities of light falling on moon from the sun due to its revolution around the Earth. Now, since the moon will have its own light, it need not to be dependent on Suns light to glow, so it will glow continuously and completely....
Read More →Paheli saw the moon through
Question: Paheli saw the moon through a glass window at 8:00 pm. She marked the position of the moon on the glass pane. She got up at 4 am in the morning. Will the moon be visible at the same position? Solution: No, Paheli will not be able to see the position of the moon at the same place because due to revolution of the moon around the earth, the position of the moon keeps on changing during the night....
Read More →Why does the moon change its shape daily?
Question: Why does the moon change its shape daily? Solution: Moon changes its shape daily because it revolves around the earth and we see only that part of the moon from which light of the sun is reflected towards us....
Read More →Meteors are not visible during
Question: Meteors are not visible during the day time. Explain the reason. Solution: Meteors are very small objects which glow due to friction when they enter the earths atmosphere. They are not visible during the daytime because their brightness is extremely small as compared to that of the sun....
Read More →A star is 10 light years away
Question: A star is 10 light years away from the earth. Suppose it brightens up suddenly today. After how much time shall we see this change? Solution: As 1 light year is the distance covered by light in one year. So, if the star which is 10 light years away from the earth glows today, then it will be seen after 10 years....
Read More →John saw full moon on a particular day.
Question: John saw full moon on a particular day. After how many days, he will be able to see the full moon again? Solution: He willbe able to see full moon gpproximately after 29 days because first, the moon size will decrease to zero, i.e. new mdcn day and then will increase from the 16th day, i.e. crescent moon will appear and finally on next 15th day, there will be a full moon again....
Read More →State whether the following are True/False.
Question: State whether the following are True/False. (i) The planet nearest to us is Jupiter. (ii)All the stars are at the same distance from us. (iii)The planets do not emit light of their own. (iv)The planets keep changing their position with respect to stars. (v) The planet Venus appears in the eastern sky before sunrise. (vi)The plane in which the earth revolves around the Sun is called equatorial plane of earth. Solution: (i) False, nearest planets to the Earth are Mars and Venus. (ii)Fals...
Read More →Prove that
Question: If $\operatorname{cosec} \theta=\frac{5}{3}$ and $\theta$ lies in Quadrant II, find the values of all the other five trigonometric functions. Solution: Given: $\operatorname{cosec} \theta=\frac{5}{3}$ Since, is in IInd Quadrant. So, cos and tan will be negative but sin will be positive. Now, we know that $\sin \theta=\frac{1}{\operatorname{cosec} \theta}$ Putting the values, we get $\sin \theta=\frac{1}{\frac{5}{3}}$ $\sin \theta=\frac{3}{5}$ (i) We know that, $\sin ^{2} \theta+\cos ^{...
Read More →Paheli and Boojho observe a bright object
Question: Paheli and Boojho observe a bright object in the night sky which was not twinkling. Paheli says, it is a star and Boojho says it is a planet. Who is correct? Solution: Boojho is correct. Only planet has the property not to twinkle, however, light due to star comes from very far distance and therefore, twinkles....
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