Newton's Second Law of Motion For Class 9

Newton's Second law of motion: It states that rate of change of momentum is directly proportional to unbalance external force. And change of momentum is in the direction of unbalance force.
Mathematical Derivation:

Initial momentum , P_i = mu
Final momentum , P_f = mv
Change in momentum ,∆p = P_f - P_i
       = mv - mu
But we know that rate of change of momentum is directly proportional to the applied unbalanced force.
∴ F ∝ ∆p/t
or F ∝ (mv - mu ) / t/
Or F ∝ m. ( v -u )/t
Or F ∝ m. a , Where a= Acceleration
Or F = k. m. a ,
Or F = 1. m. a , In SI system K=1
∴ F = m. a

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Newton's First Law of Motion Class 9 | Law of Inertia

Newton's First Laws of Motion { Law of Inertia }- It states that a body continue in its state of rest or of uniform motion until it is comepelled by any external unbalance forces.

This laws is also known as law of inertia.

Inertia is the proerty of a body which cause it to maintain its state of motion or rest.

Unbalanced Forces : When two unequal forces acts on an object and the object change its state then we say that the forces are unbalance.
Unbalance forces can be understood from example of tug of war.
Watch this video.

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List of Hindi Difficult Words

Learning Hindi is easy if we are going in right way. Many of us are struggling for Hindi learning. We already have created Youtube videos for learning hindi . However We need practice to write correctly.

This is the list of Hindi words in which a student of class 5 have created mistakes are. This is a tested list of words. I think many students do mistakes while writing these Hindi words. I suggest you to practice these words and post your mistakes if possible. There are Videos at the end for learning Hindi

उचित  पछताएगा न्याय गिर बकरी पेचिश पीलिया त्वचा योग्य मानव इकाई व्यवस्थित वर्णमाला उच्चारण व्यवस्थापना उच्चारित  इकाईयां तुम्हारे  विवाह  धृष्टता दूँगी पक्षी विशेष समाज ब्राह्मण पहरा कार्य प्राप्त खरीद

शीतल जादू स्वच्छ वायु बीमारी पढ़ने अकाल समस्याए  प्रयोग अविष्कार देवदार रसायनों आत्मकथा परिशान बचाया चंगुल कूदना भावना सहभागिता पढ़ाई निगरानी चिंता मौखिक संस्कृत इसलिए देवनागरी लिपि उचित विमाला ओतिकड़म चमत्कार उपाय सरोवर घाटी

मराठी पहाड़ी द्रव्यवाचक परिवर्तन मात मातृत्व व्यक्ति घाल छाल ईट आदि सुरक्षित आविष्कार इतिहास छिप अनुशासन बढ़ती बढ़ मुख्यमंत्री नदी मंत्रिया अचानक दीवार कर्ज शिक्षक फलस्वरूप निश्चित

Watch my channel for more Hindi videos.

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In triangle ABC, AB > AC. | E is the mid-point of BC | and AD is perpendicular to BC

In triangle ABC, AB > AC. E is the mid-point of BC and AD is perpendicular to BC.
Prove that
AB² + AC² = 2.AE² + 2.BE²

Solution: In ∆ ABD AB² = AD ² + BD ²
Or AB² = AD ² + (BE + ED ) ²
Or AB² = AD ² + BE ² + 2. BE . ED + ED ²
Or AB² = AE ² + BE ² + 2. BE . ED -----(i)
In ∆ ADC AC² = AD ² + CD ²
OR AC² = AD² + ( CE - ED) ²
Or AC² = AD² + CE ² - 2. CE . ED + ED ²
Or AC² = AE² + CE ² - 2. CE . ED ------(ii)
Adding equation 1 and situation 2 we have:
AB² + AC² = AE² + AE² + BE² + CE² + 2. BE . ED - + 2. CE . ED
Or AB² + AC² = AE² + AE² + BE² + BE² + 2. BE . ED - 2. BE . ED (As BE = CE )
∴ AB² + AC² = 2 AE² + 2BE² Proved

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