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# Displacementr, velocity and acceleration

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Suppose that the position vector for a particle is given as r=xi+yj, with x=at+b and y=ct+d, where a = 1m/s, b=1m, c=0.125m/s^2, and d=1m. a. Calculate the average velocity during the time interval from t=2.00s to 4.00s. b. Determine the velocity and the speed at t=2.00s. I can''t see where they are getting this answer. answer a. average velocity =(x(4.00) - x(2.00)/4.00s - 2.00s)i + (y4.00)-y(2.00)/4.00s - 2.00s))j =(5.00m-3.00m/2.00s)i+(3.00m - 1.50m/2.00s)j Average velocity = (1.00i+0.750j)m/s

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The average velocity is given by the change in displacement divided by the change in time.

(r2 - r1) / (t2 - t1)

= (x2 - x1)i + (y2 - y1)j / (t2 - t1)

= [(x2 - x1)/(t2 - t1)]i + [(y2 - y1)/(t2-t1)j]

Simply plug in what x and y are (at + b, ct + d) and solve, it should work out.

Hope that helps!

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I haven''t been around much lately, so maybe someone can answer a question for me. When exactly did this place change from the math/physics forum to the math/physics homework forum?

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It happens with everything as the bar is, so to speak, lowered. It''s an inevitable trend.

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It is the physics/math forum as long as it pertains to physics & math I dont see the problem.

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It''s the physics/math forum on a game development website.

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I tend to agree with Dracoliche. There have been several questions in different threads, and from a couple of different members, that have every appearance of being homework problems. That bothers me. The purpose of homework is to help you learn to solve problems for yourself. And that doesn''t mean find or steal someone else''s solution. Personally, I''m inclined to close the threads and delete the answer posts. But I will seek guidance before proceeding with this action. After all, without seeing proof, I can''t say for certain that the questions are homework questions.

I do offer this opinion to those who would post homework questions here, hoping to get an answer and make their life easier. Your education is not a free ride. You have to work for it. Otherwise, you actually have cheated yourself out of half of the education. Even if you can get away with cheating in school, it will catch up with you sometime. Will you feel good about yourself when you don''t have the problem solving skills to complete basic tasks once you eventually get a job? Do the work now, for yourself. You''ll be much more confident, and you will have those skills to be successful in life.

Graham Rhodes
Senior Scientist
Applied Research Associates, Inc.

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I''m closing this thread and several others because the question appears to be a school homework assignment from a math class. The purpose of homework is to teach students to build their comprehension of a subject and their problem-solving skills, possibly with the assistance of other students in the same class or teachers of the class. Especially for math problems such as the one posed here, it is absolutely NOT appropriate to seek the answers from folks outside one''s class or school.

These forums are to be used for assistance in game development activities only.

Graham Rhodes
Senior Scientist
Applied Research Associates, Inc.