course Phy 121 mrbߍassignment #011
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17:22:59 set 3 problems 15-19. Explain the difference between a conservative and a nonconservative force, and give an example of each.
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RESPONSE --> a nonconservative force is one that depends on the path that's taken, like if you push a box on the floor, the box's force is dependent on the friction a conservative force is one that does not depend on a certain path, like gravity confidence assessment: 3
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17:25:51 If a system does work W1 against a nonconservative force while conservative forces do work W2 on the system, what are the change in the KE and PE of the system? Explain your reasoning from a commonsense point of view, and include a simple example involving a rubber band, a weight, an incline and friction.
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RESPONSE --> the KE change would be F= W2 - W1 if you stretch a rubber band over an incline and add a weight, there is friction involved (noncon) and that would be subtracted from the work the weight does to the rubber band confidence assessment: 1
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17:26:58 If the KE of an object changes by `dKE while the total nonconservative force does work W on the object, by how much does the PE of the object change?
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RESPONSE --> the PE would change by 'dKE - W='PE confidence assessment: 1
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17:28:50 Give a specific example of such a process.
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RESPONSE --> if a cart 1 pushes another cart 2 and changes the KE by W1, then the new KE, new PE, and amount of W done would have to equal 0 when added together confidence assessment: 1
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17:31:29 Class notes #10. Why does it make sense that the work done by gravity on a set of identical hanging washers should be proportional to the product of the number of washers and the distance through which they fall? Why is this consistent with the idea that the work done on a given cart on an incline is proportional to the vertical distance through which the cart is raised?
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RESPONSE --> Wg = #Washers * 'ds and 'W on a cart is prop. to 'ds cart is raised because gravity is the constant in each case confidence assessment: 0
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17:33:43 How does the work done against friction of the cart-incline-pulley-washer system compare with the work done by gravity on the washers and the work done to raise the cart? Which is greatest? What is the relationship among the three?
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RESPONSE --> the work done on the washers is greatest becase there is no friction, with the cart there is friction the work done by gravity would be proportional to the number of washers used which would then be proportional to the distance the cart moves on the incline confidence assessment: 2
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17:36:31 What is our evidence that the acceleration of the cart is proportional to the net force on the cart?
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RESPONSE --> our evidence is Newtons 2nd Law of Motion, the more force (washers * gravity) we added to the system, the more the cart accelerated, thus proving the 2nd Law of motion confidence assessment: 2
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17:40:38 prin phy and gen phy prob 34: Car rolls off edge of cliff; how long to reach 85 km/hr?
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RESPONSE --> using the formula vf=v0 + a'dt i got it would take about 2.34s to reach 85 km/hr confidence assessment: 2
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17:42:27 **** prin phy and gen phy problem 2.52 car 0-50 m/s in 50 s by graph How far did the car travel while in 4 th gear and how did you get the result?
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RESPONSE --> 0-50m/s in 50 s is very slow and has an avg V of only 1m/s i guess in 4th gear it went slow too confidence assessment: 0
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