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Asked on 05 Apr CBSE/Class 8/Maths

Want home tuitions for STD 8th CBSE Maths and Science, who can teach concepts well?

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Asked on 28 Mar CBSE/Class 8/Science

Make a list of at least four effects of force that can be produced, when a net force acting on an object... read more
Make a list of at least four effects of force that can be produced, when a net force acting on an object is non-zero. (For class VIII students) read less

Answer

Lesson Posted on 24 Mar CBSE/Class 9/Science CBSE/Class 10 CBSE/Class 8 +2 CBSE/Class 6/Science/Motion & Measurement of Distances CBSE/Class 9/Science/Motion less

Graphical representation of motion equations

Soumi Roy

I am an experienced, qualified tutor with over 5 years of experience in teaching maths and physics across...

Equation of Motion (For Uniformly Accelerated Motion) First Equation: v = u + at Final velocity = Initial velocity + Acceleration × Time Graphical Derivation Suppose a body has initial velocity ‘u’ (i.e., velocity at time t = 0 sec.) at point ‘A’ and this... read more
Equation of Motion (For Uniformly Accelerated Motion)
 
First Equation: v = u + at
 
Final velocity = Initial velocity + Acceleration × Time
 
Graphical Derivation
 
Suppose a body has initial velocity ‘u’ (i.e., velocity at time t = 0 sec.) at point ‘A’ and this velocity changes to ‘v’ at point ‘B’ in ‘t’ secs. i.e., final velocity will be ‘v’.
For such a body there will be an acceleration.
a = Change in velocity/Change in Time
⇒ a = (OB - OA)/(OC-0) = (v-u)/(t-0)
⇒ a = (v-u)/t
⇒ v = u + at
 
Second Equation: s = ut + ½ at2
 
Distance travelled by object = Area of OABC (trapezium)
= Area of OADC (rectangle) + Area of ??ABD
= OA × AD + ½ × AD × BD
= u × t + ½ × t × (v – u)
= ut + ½ × t × at  
⇒ s = ut + ½ at (?a = (v-u)/t)
 
Third Equation: v2 = u2 + 2as
 
s = Area of trapezium OABC
⇒ v2 = u2 + 2as
Example 1: A car starting from rest moves with uniform acceleration of 0.1 ms-2 for 4 mins. Find the speed and distance travelled.
 
Solution
 
u = 0 ms-1 (? car is at rest)
a = 0.1 ms-2
t = 4 × 60 = 240 sec.
v = ?
From, v = u + at
v = 0 + (0.1 × 240)
⇒ v = 24 ms-1 
 
Example 2: The brakes applied to a car produces deceleration of 6 ms -2 in opposite direction to the motion. If car requires 2 sec. to stop after application of brakes, calculate distance travelled by the car during this time.
 
Solution
 
Deceleration, a = − 6 ms-2
Time, t = 2 sec.
Distance, s = ?
Final velocity, v = 0 ms-1 (? car comes to rest)
Now, v = u + at
Or  u = v – at
Or  u = 0 – (-6×2) = 12 ms-1
And, s = ut + ½at2
= 12 × 2 + ½ (-6 × 22)
= 24 – 12 = 12 m
 
Uniform Circular Motion
 
 
→ If a body is moving in a circular path with uniform speed, then it is said to be executing uniform circular motion.
 
→ In such a motion the speed may be same throughout the motion but its velocity (which is tangential) is different at each and every point of its motion. Thus, uniform circular motion is an accelerated motion.
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Lesson Posted on 06 Mar CBSE/Class 8

English Exercice 1

Sujoy D.

1. Strong concept building classes. 2. Weekly tests in weak areas for students to improve their confidence. 3....

Question Answer: Explanation:In Short , we have trouble holding very large numbers in our minds, like thousands and above. Guessign game suggests that we have problems is estimation hundreds too. Let us eliminate now: [2], which says that it is 'impossible' for us to imagine numbers above a hundred,... read more

Question

Answer:

Explanation:

In Short , we have trouble holding very large numbers in our minds, like thousands and above. Guessign game suggests that we have problems is estimation hundreds too.

Let us eliminate now:

[2], which says that it is 'impossible' for us to imagine numbers above a hundred, is too extreme.

[3], which talks only about millions and more, is incorrect.

[4] wrongly describes the guessing game.

Hence, [1].

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Lesson Posted on 06 Mar CBSE/Class 8

English Exercise 2

Sujoy D.

1. Strong concept building classes. 2. Weekly tests in weak areas for students to improve their confidence. 3....

Question: Answer: It seems to be a difficult one to read and understand. Never mind, look at the options and eliminate one by one:Rupert Baxter was Lord Emsworth's former secretary not current one, So [2] is eliminated, [4] implies the opposite of what is said in passage. The passage talks... read more

Question:

Answer:

It seems to be a difficult one to read and understand. Never mind, look at the options and eliminate one by one:

Rupert Baxter was Lord Emsworth's former secretary not current one,

So [2] is eliminated,

[4] implies the opposite of what is said in passage.

The passage talks only about Lord Emsworth's dislike of Rupert Baxter, and not vice versa, so [1], which states that they both disliked each other, is incorrect.

Hence, [3].

 

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Lesson Posted on 06 Mar CBSE/Class 8

English Exercise 3

Sujoy D.

1. Strong concept building classes. 2. Weekly tests in weak areas for students to improve their confidence. 3....

Question: Answer: Let us eliminate:[1] fails to mention an important point: that the reason people cannot understand the machines that engineers design is that these machines are too logical. [2] wrongly states that engineers 'know' that other people are not always logical. Option [4] states... read more

Question:

Answer:

Let us eliminate:

[1] fails to mention an important point: that the reason people cannot understand the machines that engineers design is that these machines are too logical.

[2] wrongly states that engineers 'know' that other people are not always logical.

Option [4] states that engineers have trouble designing logical machines, which contradicts the paragraph.

Hence, [3].

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Lesson Posted on 06 Mar CBSE/Class 8

Give Some Uses Of LED. How Should LED Be Connected?

Sujoy D.

1. Strong concept building classes. 2. Weekly tests in weak areas for students to improve their confidence. 3....

Question: Give some uses of LED. How should LED be connected? Answer: (a) As indicators in electrical appliances. (b) As a point source of light in laser beam torches. (c) LEDs emitting white light can be used instead of bulbs. The longer lead (leg) from the LED should be connected to the positive... read more

Question:

Give some uses of LED. How should LED be connected?

Answer:

(a) As indicators in electrical appliances.

(b) As a point source of light in laser beam torches.

(c) LEDs emitting white light can be used instead of bulbs. The longer lead (leg) from the LED should be connected to the positive terminal of the battery and the shorter lead to the negative terminal of the battery.

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Lesson Posted on 06 Mar CBSE/Class 8

Give Methods By Which Pollution Due To Plastics Can Be Solved.

Sujoy D.

1. Strong concept building classes. 2. Weekly tests in weak areas for students to improve their confidence. 3....

Question: Give methods by which pollution due to plastics can be solved. Answer: Pollution due to plastics can be solved by following methods: (a) Avoid the use of plastics as far as possible. (b) Use bags, made of jute or cloth. (c) Biodegradable and non-biodegradable wastes should be separated... read more

Question:

Give methods by which pollution due to plastics can be solved.

Answer:

Pollution due to plastics can be solved by following methods:

(a) Avoid the use of plastics as far as possible.

(b) Use bags, made of jute or cloth.

(c) Biodegradable and non-biodegradable wastes should be separated and disposed off separately.

(d) Plastics should be recycled and reused.

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Lesson Posted on 06 Mar CBSE/Class 8

A Wants To Study The Chemical Effect Of Current At Home. How Can He Do It?

Sujoy D.

1. Strong concept building classes. 2. Weekly tests in weak areas for students to improve their confidence. 3....

Question: A is wants to study the chemical effect of current at home. How can he do it ? Answer: A can study the chemical effect of current at home very easily. Take two pieces of copper wire and iron wire. Place them in fresh lemon fruit. Attach the free ends of the wires to a LED. LED glows showing... read more

Question:

A is wants to study the chemical effect of current at home. How can he do it ?

Answer:

A can study the chemical effect of current at home very easily. Take two pieces of copper wire and iron wire. Place them in fresh lemon fruit. Attach the free ends of the wires to a LED. LED glows showing the flow of current.


dinesh-is-wants-to-study-the-chemical-effect-of-current-at-home-how-can-he-do-it-2

 

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Lesson Posted on 06 Mar CBSE/Class 8

Even Though Plastics Are Very Useful, They Are Not Environment Friendly

Sujoy D.

1. Strong concept building classes. 2. Weekly tests in weak areas for students to improve their confidence. 3....

Question: Even though plastics are very useful, they are not environment friendly.” Justify the statement Answer: Plastics are very useful, but their disposal is a big problem. Plastics are non-biodegradable and take many years to decompose. They release a lot of poisonous fumes, when burnt... read more

Question:

Even though plastics are very useful, they are not environment friendly.” Justify the statement

Answer:

Plastics are very useful, but their disposal is a big problem. Plastics are non-biodegradable and take many years to decompose. They release a lot of poisonous fumes, when burnt so they cause environmental pollution.

Question:

What is the difference between current flowing through metals and current flowing through liquids?

Answer:

In metals electric current is conducted by flow of electrons. In liquids, the movement of charged particles (ions) carry current from anode to cathode terminals. Electrolytes conduct
current at a slow rate than metals.

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