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Announcements

Announcements. Midterm-I is on Thursday (Feb. 10 th ) between 5:30-6:30 pm. Topics included are Chapters 1, 2, and 3 STUDY GUIDE is available in the course home page at http://physics.okstate.edu/babu/2014

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Announcements

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  1. Announcements • Midterm-I is on Thursday (Feb. 10th) between 5:30-6:30 pm. Topics included are Chapters 1, 2, and 3 • STUDY GUIDE is available in the course home page at http://physics.okstate.edu/babu/2014 • A formula sheet will provided to you during the test. For further details see the study guide • Those who don’t have access to web can download the study guide from library or can come by during the office hours to pickup a copy • All HW solutions should be available on the web for you to study them for the test • HW4: (Chapter 4): 4, 6, 9, 12, 28, and 34 (a, b, c) Due: Feb 18th. • There would not be regular class meeting on the exam day (02/10/05) but, I will review the exam material. Those interested may attend

  2. Chapter 4 (contd.) : Newton’s Laws • In the light of various types of forces, we will attempt to address the following questions • What does a Force do? – A virtual experiment • How does an object move when an external force is applied? • Are there additional relationships between Force and motion? – Newton’s Laws • What is the “natural state” of an object? – the beginning of physics! • Mass – definition of • Free body diagrams

  3. What do forces do? Stretching of N rubber bands require a net force of NF

  4. Effect of Force – A virtual experiment • Pull the block of mass with different F values and note down a • Plot F versus a • Observer that F is proportional to a • Slope of the graph is a constant • Observation: a F

  5. Does the accelerationdepend on the size of an object? • Plot dependence of a for different values of F • Observe that the slope of the graph changes with size of the object • If size of the object is proportional to the matter it contains, slope is inversely proportional to the size of the object • Loosely speaking, the size of the matter is defined as “mass” of the object • Mass  1/C and C  (a/F)

  6. Stop to Think • What do you mean by the size of the object? • What is the relationship between the slope of F versus a graph? • Does the slope depend on the size of an object? • Is there a better way of describing the size of an object? • Is the shape of an object relevant? • Can we put both size and shape into a single entity?

  7. ~ F ~ t n e a = m Newton’s Second Law • An object of mass “m” subjected by a net force F experiences an acceleration a in the direction of the net Force F Basic unit of Force is Newton and is denoted by N 1N = 1kg x 1m/s2 1lb weight = 4.45 N

  8. Example • Two forces (T1,T2) are acting on an object of mass “m” • The direction of net force can be obtained by applying the parallogram theorem

  9. Free body diagram (FBD)

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