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Unformatted text preview: Today Today ’ ’ s Lecture s Lecture Review of Newton’s 3 rd Law & Hook’s Law Application of Newton’s Laws: Friction Lecture 9 Example: Using Newton Example: Using Newton ’ ’ s Third Law s Third Law A 12N force is applied to left most of a 1kg , 2kg , and a 3kg block as shown. (a) What force does the middle block exert on the rightmost block, F 23 ? From Newton’s 2 nd , the acceleration of all of the blocks is: a F / m tot 12 N /6 kg 2 m / s 2 Hence the force from the middle block on the 3 rd block is given by: F 23 m 3 a 3 2 6 N Example: Using Newton Example: Using Newton ’ ’ s Third Law s Third Law A 12N force is applied to left most of a 1kg , 2kg , and a 3kg block as shown. (b) What force does the first block exert on the middle block? The acceleration of all of the blocks is a = 2m/s 2 . The net force of the middle block can also be determined from Newton’s 3 rd and Newton’s 2 nd : From Newton’s 3 rd F 23 = 6N . Hence F 1 is given by: F 1 net F 12 F 32 F 12 − F 23 m 2 a 2 2 4 N F 12 F 23 F 1 net 6 4 10 N Example: Using Newton Example: Using Newton ’ ’ s Third Law s Third Law A 2200kg plane is pulling two gliders down the runway with an acceleration of 1.9m/s 2 . The first glider has a mass of 310kg and the second 260kg . (a) Find the horizontal thrust of the plane’s propeller. From Newton’s 2 nd , the thrust is: (b) Find the tension in the first rope. F thrust m tot a 310 260 2200 1.9 5263 N Since the only force on the first glider is the tension in the first rope, from Newton’s 2 nd we have: T 1 m 1 a 310 1.9 589 N Example: Using Newton Example: Using Newton ’ ’ s Third Law s Third Law A 2200kg plane is pulling two gliders down the runway with an acceleration of 1.9m/s 2 . The first glider has a mass of 310kg and the second 260kg ....
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This note was uploaded on 04/16/2008 for the course PHYS PHYS2A taught by Professor Hicks during the Spring '08 term at UCSD.
 Spring '08
 Hicks
 Force, Friction

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