Scientific Study
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Given reason:
(a) Joule is the derived unit of work.
→ Because Joule is defined in terms of other fundamental units. specially the newton (N) for force and meter (m) for distance.
(b) Some variables should be controlled while performing on experiment.
→ Because to ensure that the observed results are solidly due to the changes in the independent variable being tested.
(c) V2 = ut is not a valid relation.
→ Because the dimensions on both sides of the equation are not consistent and it does not derive from any standard kinematic equation.
Differentiate between:
(a) Independent variable and Dependent variable
| Independent variable | Dependent variable |
|---|---|
| The variable which is changed or manipulated in on experiment. | The variable that is observed or measured in response. |
| Cause or input. | Effect or output. |
| It doesn’t depend on any factor. | It depends on independent one. |
| Eg: Amount of water given to plant. | Eg: Growth of plant. |
(b) Fundamental unit and derived unit
| Fundamental unit | derived unit |
|---|---|
| Basic units that are not derived from other units. | Units that are derived from fundamental units. |
| There are 7 fundamental units. | Many derived units can be formed from fundamental unit. |
| Independent cannot be broken into other units. | It can be broken into fundamental units. |
| Eg: kilogram, second etc. | Eg: Newton, pascal, Joule etc. |
Answer these questions:
(a) What is a unit?
→ The unknown quantity which is used in measurement is known as unit.
(b) Write the SI units of mass, temperature, energy and density.
→ The SI unit of mass, temperature, energy and density are:-
- mass: kg
- temperature: K
- energy: J
- density: kg/m3.
(c) How is the validity of on equation checked? Write on example?
→ If the right hand side of equation and left hand side equation are equal then the equation is valid. Example: While performing the unit analysis of the equation:
(d) Mention the fundamental units involved in the unit of pressure.
→ The fundamental units involved in the unit of pressure are:-
(e) Find out the fundamental units involved in the given derived unit.
(f) Niva claimed that on alternative formula for power is P = mv2 and the formula of pressure; P = mv/A. check the validity of given formulae by the analysis of units.
→ For,
L.H.S
R.H.S.
This formula is not valid
L.H.S.
R.H.S.
This formula is not valid.
(g) Describe the independent variable, dependent variable and controlled variable with a suitable example of each.
→ (a) Those variables which can be changed during a experiment of scientific study is known as independent variable.
(b) Those variables whose value depends upon the value of another variable is known as dependent variable.
(c) The variable which are same in every experiment to keep the value same is known as controlled variable.
Now,
For subject:
Relation of a rotating knob of a tap and the rate of flow of the water.
Examples:
magnitude of rotating of knob (in degree).
Amount of the water flow per minute (in liters).
water pressure.
(h) Karma connected a dry cell to a bulb using a few pieces of wire and lit the bulb. He was curious to know how the thickness of the used wire affects the life span of a dry cell. In this test or experiment, find out the independent variable, dependent variable and controlled variable.
→ In this synerio:
(i) chodoni wanted to investigate the effects of substance mixed with the soil on plant grown.
She decided to mix lime, urea fertilizer, common soil, and compost manure in the soil. Then she brought a bucket of soil from a nearby field and sieved it. she put that soil equally into 12 uniform sized pots. Then she mixed two spoons of salt in every three pots, two spoons of urea fertilizers in each of the next three pots, and finally, two spoons of compost fertilizer in each of the remaining three pots. She then planted similar seeds of
the same plant in every pot and placed them all in a sunny place in the house. she watered all the pots everyday. After the plants grew, she measured the height of each plant daily and kept a record.
i) Identify the independent variable, dependent variable and controlled variable in chondoni’s experiment.
ii) Why did chondoni use 3 pots for each experiment?
(i) ans The independent variables are:
- Amount of substance.
- sunlight.
- water.
The dependent variable are:-
- The height of plant.
- The growth of plant.
The controlled variable are:-
- Amount of soil.
- similar seeds.
ii) ans chondoni use 3 pots for each experiment because, there are 12 pots and 4 substance which can be equally divided
into 3 pots that makes the observation more accurate.
(j) subodh wanted to know how the colour of an object affects its ability to hold heat.
For that he took four conical flasks and coated the first flask with black coloured enamel the second with white enamel the third with green enamel and the fourth with red enamel. Then, he filled all the flask with water, closed the mouth of each flask tightly with cork and then kept them in the sun. After some times he measured the temperature of water in each flask with the help of a thermometer and noted the readings.
Identify the independent variable and dependent variable in subodh’s experiment. which variable should be controlled by subodh?
→ In the experiment;
• The colours enamel in the flasks.
• The noted readings with the help of thermometer.
The controlled variable in this experiment is the amount of heat and the amount of water given in the flasks.
(k) manisha wanted to test the eating habits of her dog. she decided to study how the amount of food and the time of giving food affects the speed at which the dog ate what is wrong with the desing of manisha’s experiment and how can she correct it.
→ The wrong thing with the design of manisha’s experiment was tho time of giving different foods item to the dogs & speed of dog. so, she should give the same food item at the same time to the dog. Through which she can study about the eating habits and speed of her dog.
(l) prove that, unit of electric resist ohm (Ω) = kg m2 s−3 A−2
→ we have,
Ohm’s law states that:
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