Find the angle in radians as well as in degrees through which a pendulum
Question: Find the angle in radians as well as in degrees through which a pendulum swings if its length is 45 cm and its tip describes an arc of length 11 cm Solution: We know that l = r Here $I=$ length of $\operatorname{arc}=11 \mathrm{~cm}$ $\mathrm{R}=$ radius $=$ length of pendulum $=45 \mathrm{~cm}$ We need to find $\theta$ $11=45 \times \theta$ $\theta=\frac{11}{45}$ radian $\theta$ in degree $=\frac{11}{45} \times \frac{180}{\pi}=\frac{44}{22 / 7}=14^{\circ}$...
Read More →An electric current is passed
Question: An electric current is passed through a conducting solution. List any three possible observations. Solution: Three possible observations are * (i) The colour of the solution may change depending upon the electrodes. (ii)The temperature of the solution may increase. (iii)Bubbles near the electrodes can be seen....
Read More →Why is tin electroplated on iron
Question: Why is tin electroplated on iron to make cans used for storing food? Solution: Electroplating of tin is done on the iron to make cans used for storing food because tin is less reactive than iron. Coating of tin prevents food from coming in contact with iron and thus, prevents it from getting spoiled....
Read More →Paheli wants to deposit silver on an iron spoon.
Question: Paheli wants to deposit silver on an iron spoon. She took silver nitrate (AgNO3) solution in a beaker and set up a simple circuit for electroplating. Which terminal of the battery should the spoon be connected to? What mjjterial should the other electrode be made of? Solution: Spoon should be connected to the negative terminal of the battery. The other electrode should be made of silver, so that silver ions get deposited on an iron spoon....
Read More →In a circle of diameter 30 cm, the length of a chord is 15 cm.
Question: In a circle of diameter 30 cm, the length of a chord is 15 cm. Find the length of the minor arc of the chord. Solution: Diameter = 30 cm Length of chord $=15 \mathrm{~cm}$ Radius $=15 \mathrm{~cm}[\mathrm{r}=0.5 \times$ diameter $]$ Since the radius is equal to the length of the chord Hence the formed triangle in the circle is an equilateral triangle. $\theta=60^{\circ}$ We know that $\mathrm{I}=\mathrm{r} \times \theta$ $I=15 \times 60 \times \frac{\pi}{180}=5 \times \pi=5 \times 3.14...
Read More →Name the effect of current responsible
Question: Name the effect of current responsible for the glow of the bulb in an electric circuit. Solution: Heating effect of electric current is responsible for the bulb to glow in an electric circuit. Due to heating effect, the filament of the bulb gets heated to a high temperature and it starts glowing....
Read More →Will the solution of sugar in
Question: Will the solution of sugar in distilled water conduct electricity? Solution: No, the solution of sugar in distilled water is a poor conductor of electricity and therefore current cannot pass through it....
Read More →Find the degree measure of the angle subtended at the centre of a circle of
Question: Find the degree measure of the angle subtended at the centre of a circle of diameter 60 cm by an arc of length 16.5 cm. Solution: Angle in radians $=$ Angle in degrees $\times \frac{\pi}{180}$ $\theta=\frac{1}{r}$ where $\theta$ is central angle, $l=$ length of arc, $r=$ radius Now, $\theta=\frac{1}{r}$ and $r=0.5 \times$ diameter $=\frac{16.5}{30}$ radians $\theta$ in degrees $=\frac{16.5}{30} \times \frac{180}{\pi}=\frac{16.5}{30} \times \frac{180}{22 / 7}=\frac{16.5}{30} \times \fra...
Read More →Why is a layer of zinc
Question: Why is a layer of zinc coated over iron? Solution: Layer of zinc is coated over iron because zinc prevents it from rust and corrosion....
Read More →Fill in the blanks.
Question: Fill in the blanks. (i) The object to be electroplated is taken as.electrode. (ii)One of the most common applications of chemical effect of electric current is. (iii)Small amount of a mineral salt present naturally in water makes it a. of electricity. (iv)Electroplating of. is done on objects like water taps and cycle bell to give them a shiny appearance. Solution: (i)NegativeThe object to be electroplated is taken as negative electrode or cathode, so that the free ions get deposited o...
Read More →Which of the following metals
Question: Which of the following metals is used in electroplating to make objects appear shining? (a) Iron (b) Copper (c) Chromium (d) Aluminium Solution: (c) Chromium is used for electroplating to make objects appear shining because chromium has a shiny appearance and it resists scratches....
Read More →Which one of the following solutions
Question: Which one of the following solutions will not conduct electricity? (a) Lemon juice (b) Vinegar (c) Tap water (d) Vegetable oil Solution: (d) Vegetable oil will not conduct electricity because it does not make ions easily....
Read More →If the arcs of the same length in two circles subtend angles
Question: If the arcs of the same length in two circles subtend angles $75^{\circ}$ and $120^{\circ}$ at the centre, find the ratio of their radii Solution: Angle in radians $=$ Angle in degrees $\times \frac{\pi}{180}$ $\theta=\frac{1}{r}$ where $\theta$ is central angle, $l=$ length of arc, $r=$ radius Therefore $\theta_{1}=75 \times \frac{\pi}{180}=\frac{5 \pi}{12}$ $\theta_{2}=120 \times \frac{\pi}{180}=\frac{2 \pi}{3}$ $I=r \times \theta$ Now, as the length is the same Therefore, $r_{1} \ti...
Read More →When electric current is passed through
Question: When electric current is passed through a conducting solution, there is a change of colour of the solution. This indicates (a) the chemical effect of current (b) the heating effect of current (c) the magnetic effect of current (d) the lightning effect of current Solution: (a) The passage of an electric current through a conducting solution causes chemical reactions. As a result, change of colour of solution occurs. This indicates the chemical effect of current....
Read More →Boojho’s unde has set up an electroplating
Question: Boojhos unde has set up an electroplating factory near his village. He should dispose off, the waste of the factory (a) in the nearby river (b) in the nearby pond (c) in the nearby corn field (d) according to the disposal guidelines of the local authority Solution: (d) In electroplating factory, the disposal of the used conducting solution is a major concern because it is a polluting waste, therefore it should be disposed off according to the disposal guidelines of the local authority....
Read More →Find the length of an arc of a circle of radius 14 cm which subtends an angle
Question: Find the length of an arc of a circle of radius 14 cm which subtends an angle of $36^{\circ}$ at the centre Solution: Angle in radians $=$ Angle in degrees $\times \frac{\pi}{180}$ Angle in radians $=$ Angle in degrees $\times \frac{\pi}{180}$ $\theta=\frac{1}{r}$ where $\theta$ is central angle, $l=$ length of arc, $r=$ radius Therefore angle $=36 \times \frac{\pi}{180}=\frac{\pi}{5}$ Now, $I=r \times \theta$ $=14 \times \frac{\pi}{5}=14 \times \frac{22}{35}=\frac{44}{5}=8.8$ Therefor...
Read More →An electric current can produce
Question: An electric current can produce (a) heating effect (b) chemical effect (c) magnetic effect (d) chemical, heating and magnetic effects Solution: (d) When an electric current is passed through a conducting solution, it causes chemical reactions. The resulting effect is called chemical effect of current. When an electric current is passed through a bulb, its filament gets heated to a high temperature and bulb starts glowing. The resulting effect is heating effect of current. Whenever an e...
Read More →Suggest three measures to
Question: Suggest three measures to limit noise pollution in your locality. Solution: The following measures to limit noise pollution in our locality is given as: (i) The industries which produce noise should be setup away from the residential areas. (ii)The television and the music systems should be run at the low volumes. (iii)The aircraft engines, transport vehicles, industrial machines and home appliances must be installed with siltncing devices....
Read More →Find the radius of a circle in which a central angle of 450
Question: Find the radius of a circle in which a central angle of $45^{\circ}$ intercepts an arc of length 33 cm. (Take $\pi=22 / 7$ ) Solution: Angle in radians $=$ Angle in degrees $\times \frac{\pi}{180}$ $\theta=\frac{1}{r}$ where $\theta$ is central angle, $l=$ length of arc, $r=$ radius Therefore angle $=45 \times \frac{\pi}{180}=\frac{\pi}{4}$ Now, $r=\frac{1}{\theta}$ $=\frac{33}{\pi / 4}=\frac{132}{22 / 7}=\frac{924}{22}=42$ Therefore radius is $42 \mathrm{~cm}$...
Read More →The town hall building is situated
Question: The town hall building is situated close to Boojhos house. There is a clock on the top of the townhall building which rings the bell every hour. Boojho has noticed that the sound of the clock appears to be much clearer at night. Explain. Solution: We know that speed, pitch, loudness all are initiated with a vibration. During the day, there is a number of vibrations around us. So, the sound coming from the clock gets disturbed and amplitude of vibrations becomes small. But during the ni...
Read More →How is sound produced and
Question: How is sound produced and how is it transmitted and heard by us? Solution: Sound is produced when any object starts vibrating by any means. These vibrations travel from the source all around the environment through the particles of the environment, thus, it reaches to its destination, i.e. our ear. Now, it enters our ear and travels down a canal at the end of which a thin membrane is stretched tightly known as eardrum. The eardrum sends vibrations to inner part of the ear and finally r...
Read More →We have a stringed musical instrument.
Question: We have a stringed musical instrument. The string is plucked in the middle first with a force of greater magnitude and then with a force of smaller magnitude. In which case would the instrument produce a louder sound? Solution: It will create more loud sound in case of string stretched with a greater force because amplitude is greater in this case and loudness depends on the amplitude. Greater will be the loudness, greater will be the amplitude....
Read More →The difference between the two acute angles of a right triangle is
Question: The difference between the two acute angles of a right triangle is $\left(\frac{\pi}{5}\right)^{\mathrm{c}}$ Solution: The angle in degree $=\frac{\pi}{5} \times \frac{180}{\pi}=36^{\circ}$ $=36^{\circ}$ Let, two acute angles are x and y So, ATQ, $x-y=36^{\circ} . .$ $x+y=90^{\circ} \ldots \ldots(2)$ Solving 1 2, we get; $\Rightarrow 2 x=126^{\circ}$ $\Rightarrow x=63^{\circ}$ Putting the value of x in 2, we get; $\Rightarrow 63^{\circ}+y=90^{\circ}$ $\Rightarrow y=27^{\circ}$ So, Two ...
Read More →List three sources of noise
Question: List three sources of noise pollution in your locality. Solution: Sources of noise pollution gre . (i) Horns of vehicles (ii)Loudspeakers of temples (iii)Generators running without silencers...
Read More →Two astronauts are floating
Question: Two astronauts are floating close to each other in space. Can they talk to each other without using any special device? Give reasons. Solution: No, they cannot talk to each other without using any special device because there is no medium in space and sound needs medium to travel....
Read More →