Can anyone provide me answers of experiment no. 1 of science journal 9th Std (Msb)
I expect someone to answer...
Im giving away 98 points!!!!!!
Answers
Answer:
is this your answer or not ........
Answer:
1. Mention the two precautions to determine the boiling point of water in laboratory.
Answer.
(i) The position of bulb should be slightly above the water level.
(ii) Stir the water continuously in beaker so that temperature should remain constant
2. The frequency of a source of sound is 100 Hz. How many times does it vibrate in a minute?
Answer.
Number of vibrations produced in 1s = 100
Number of vibrations produced in 60 sec = 100 × 60 = 6000
Now, 1 minute = 60 seconds
Thus, number of vibrations produced in one minute = 6000
3. In which of the two, glycerine or kerosene, the loss in weight of a solid when fully immersed in them will be more and why ?
Answer.
Density of glycerine is more than that of kerosene.
A liquid having higher density exerts more upthrust force on object than other liquid having low density. Thus, greater the density of a liquid, the more will be the the buoyant force exerted on the object immersed in it. Now, due to this greater upthrust (buyont force), the object experiences greater apparent weight loss
.
Thus in case of glycerine, the loss in weight of a solid when fully immersed in it will be more than when immersed in kerosene.
4. A sound wave travels at a speed of 340m/s. If its wavelength is 2 cm, what is the frequency of the wave? Will it be in the audible range?
Answer.
It is given that,
Velocity of sound, v = 340 m/s
Wavelength, λ = 1.4 m
Frequency, ν =?
We know that, speed = wavelength × frequency
⟹ 340 = 1.4 x ν
⟹ ν = 340/1.4 = 242.86 Hz
As the audible range is between 20 Hz – 20,000 Hz
Here, 242.86 Hz < 20,000 Hz
Therefore it is in the audible range.
5. When dipped in a fluid, name the factor on which the loss in weight of a solid depends. Name the two forces which act upon the solid dipped in the fluid.
Answer.
Loss in weight of a solid dipped in a fluid depends upon the density of that fluid.
The two forces which act upon the solid dipped in the fluid are:
True weight of the body acting vertically downwards.
Buoyant force or upward thrust acting vertically upwards.
6. In an experiment to determine the boiling point of water, state reason for the following:
(i) Pumice stone pieces are added to water in the beaker.
(ii) A glass stirrer is used.
Answer.
(i) Pumice stone is added to avoid any bumping of water. When the temperature is raised for boiling the water, it starts to bump. But pumice stone being porous, provides space for air. This reduces bubbling in hot water to facilitate the boiling process.
(ii) A glass stirrer is used to ensure uniform heating of water.
7. A mixture of sand, powdered glass and common salt is dissolved in water and then filtered. Name the substance left on filter paper. Name the substance in the filtrate.
Answer.
Out of the given three substances only common salt is soluble in water whereas both sand and powdered glass are insoluble in water. Thus when a mixture of sand, powdered glass and common salt is dissolved in water and then filtered sand and powdered glass would be left on filter paper while common salt will be present in the filtrate.
8. A free falling object eventually stops on reaching the ground. What happens to its kinetic energy?
Answer.
Its kinetic energy will be zero on reaching the ground. Actually, when an object falls freely towards the ground, its potential energy decreases and kinetic energy increases. But as soon as the object touches the ground, all its potential energy gets converted into kinetic energy and finally when the ball stops after hitting the ground, all its kinetic energy gets converted into heat energy and sound energy.
9. Name the adaptation of fish which helps it in each of the following:
(i) Swimming in water
(ii) Breathing
Answer.
(i) Fish have fins for swimming in water.
(ii) They have gills for breathing in water.
10. A baby is not able to tell her/his caretakers that she/he is sick. What would help us to find out that the baby is sick?
Answer.
Behavioural changes like constant crying, irritabilty, improper intake of food, low period of activeness and mood swings can help to determine that the baby is sick.