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# Ch2 HW2 - WebAssign Ch2 HW2 2008(Homework Current Score 21...

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Ch2 HW2 2008 (Homework) Arthur Barfield PHYS 2211, section M, Fall 2008 Instructor: Jennifer Curtis Web Assign Current Score: 21 out of 24.5 Due: Friday, August 29, 2008 09:00 AM EDT Description Updating position if momentum is changing; Constant force; Graphs of motion Instructions Reading: Sec 2.4-2.5 Because problems 2 and 5 require a long chain of calculations, six submissions are permitted for these problems. For problem 1 (multiple choice), only two submissions are permitted. The due date for this assignment is past. Your work can be viewed below, but no changes can be made. 1. [MI2 02.RQ.16] 1/1 points The x component of the momentum of an object is observed to increase with time: At t = 0 s, = 30 kg · m/s At t = 1 s, = 40 kg · m/s At t = 2 s, = 50 kg · m/s At t = 3 s, = 60 kg · m/s What can you conclude about the x component of the net force acting on the object during this time? is zero. Not enough information is given. is decreasing with time. is constant. is increasing with time. Solution or Explanation The change in momentum is the same over every time interval.

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2. [MI2 02.P.26] 3/4.5 points A ping-pong ball whose mass is 0.0027 kg ( 2.7 g) is acted upon by the Earth and the air (there is air resistance, and there is also a strong wind). This table gives the position of the ball at several times: Time Position 12.35 s < 3.17 , 2.54 , -9.38 > m 12.39 s < 3.25 , 2.50 , -9.40 > m ... ... 14.35 s < 9.37 , -0.66 , -10.40 > m 14.39 s < 9.54 , -0.75 , -10.42 > m What was the average momentum of the ball during the earlier time interval, from t = 12.35 s to 12.39 s? = < .0054 0.0054 , -.0027 -0.0027 , -.00135 -0.00135 > kg · m/s What was the average momentum of the ball during the later time interval, from t = 14.35 s to 14.39 s? = < .01145 0.0115 , -.0061 -0.00607 , -.00135 -0.00135 > kg · m/s In the time interval from 12.35 s to 14.35 s, what was the average net force acting on the ball? = < (No Response) 0.00304 , (No Response) -0.00169 , (No Response) 0 > N Solution or Explanation Apply the Momentum Principle to find the average net force. 3. [MI2 02.X.07.01] 2/2 points (a) A runner starts from rest and in 3 s reaches a speed of 9 m/s. If we assume that the speed changed at a constant rate (constant net force), what was the average speed during this 3 s interval?
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Ch2 HW2 - WebAssign Ch2 HW2 2008(Homework Current Score 21...

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