Lecture#4 - Chapter 3 Explaining Motion Lecture #4: 1. 2....

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Chapter 3 Explaining Motion Lecture #4: 1. Newton’s Second Law 2. Mass and Weight 3. Friction 4. Newton’s Third Law of Motion 1. Newton’s Second Law of Motion In the previous lecture we have learned that if an object is acted upon by a net force, then it experiences acceleration. Newton’s second law allows us to calculate this acceleration. The value of this acceleration is proportional to the size of the unbalanced force and inversely proportional to the object’s mass. The direction of acceleration is the same as that of the unbalanced force. If the unbalanced force is larger, then the object will experience more acceleration. However, if the object is heavier, then the acceleration will be small. This situation is getting complicated in words; let us use some mathematics to calculate size of the acceleration. If we denote the unbalanced force by F , mass of the object by m , and acceleration by a , Then we can express acceleration as Combining together we get Rearranging the equation, we get This is the well-known form of the Newton’s second law. In words it means that net force on an object equals mass of the object multiplied with the acceleration, and is pointed in the direction of acceleration.
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Example: A net force of 6N acts in the northerly direction on a mass of 2 Kg. What is the acceleration of the mass? Solution: As we have learned Example: What is the net force needed to accelerate a 5 Kg object at 3 m/sec 2 . Solution: Applying Newton’s second law Note: If you look at the second law carefully, then you will conclude that the first law is a special case of the second law when net force F = 0. This implies that either mass or the
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This note was uploaded on 06/03/2011 for the course PHYSICS 1010 taught by Professor Fsomething during the Spring '11 term at UConn.

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Lecture#4 - Chapter 3 Explaining Motion Lecture #4: 1. 2....

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