course phy201 Dave,Two questions:
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14:26:57 Explain how to obtain the final speed and direction of motion of a projectile which starts with known velocity in the horizontal direction and falls a known vertical distance, using the analysis of vertical and horizontal motion and vectors.
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RESPONSE --> The projectile takes a parabolic path. It's horizontal velocity is constant. It drops in the vertical direction at the acceleration of gravity. Using the formulas of uniformly acceerated motion you can easily calculate the time to hit the ground using ds=v0*t +1/2*g*t^2 and we can also find it's vertical position for any other dt. The horizontal movement is simple since velocity is constant. Each point will have a horizontal vector that is the same throughout but the vertical vector grows as the objects path, following the parabolic function, becomes closer to vertical.
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14:29:17 ** The horizontal velocity is unchanging so the horizontal component is always equal to the known initial horizontal velocity. The vertical velocity starts at 0, with acceleration thru a known distance at 9.8 m/s^2 downward. The final vertical velocity is easily found using the fourth equation of motion. We therefore know the x (horizontal) and y (vertical) components of the velocity. Using the Pythagorean Theorem and arctan (vy / vx) we find the speed and direction of the motion. **
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RESPONSE --> ok Enter, as appropriate, an answer to the question, a critique of your answer in response to a given answer, your insights regarding the situation at this point, notes to yourself, or just an OK. Always critique your solutions by describing any insights you had or errors you makde, and by explaining how you can make use of the insight or how you now know how to avoid certain errors. Also pose for the instructor any question or questions that you have related to the problem or series of problems.
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14:31:49 Give at least three examples of vector quantities for which we might wish to find the components from magnitude and direction. Explain the meaning of the magnitude and the direction of each, and explain the meaning of the vector components.
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RESPONSE --> Velocity, force, momentum are three examples of vector quantities. by graphing the vector on an X,Y grid and using some simple trig we can find the X and Y components of the vector and by doing so calculate the magnitude and direction of the vector under study.
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14:32:11 ** GOOD STUDENT RESPONSE: Examples might include: A force acting on an object causing it to move in an angular direction. A ball falling to the ground with a certain velocity and angle. A two car collision; velocity and momentum are both vector quantities and both important for analyzing the collision.. The magnitude and directiohn of the relsultant is the velocity and direction of travel. The vector components are the horizontal and vertical components that would produce the same effect as the resultant.
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RESPONSE --> ok
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