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Midterm-I on Feb. 10th. Study guide available online. Formula sheet provided during test. Homework solutions online. Exam review on exam day. Topics include force, motion, Newton's Laws, free body diagrams. Attend review session for Chapter 4. Additional relationships between force and motion explored.
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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
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
What do forces do? Stretching of N rubber bands require a net force of NF
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
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)
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?
~ 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
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