course Phy 231 I did not forget to do the lab for assignment 21, I will do that shortly. ???{?????????vassignment #021
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09:27:24 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 --> We first find the final velocity in the y direction: vf^2 = v0^2 + 2ads, We then have a vf in y direction. The vf in the horizontal direction will not change. The magnitude of the vf would be: magnitude=sqrt((vertical vf)^2 + (horizontal vf)^2). The direction of the vf would be arctan(vertical vf/horizontal vf).
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09:27:48 ** 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
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09:40:21 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 --> 1) If a ball is thrown off a tall building with an inital horizontal velocity but with no initial vertical velocity and we're trying to find vf. We find vf by finding the magnitude of of each x and y component and then use the eqn: magnitude=sqrt(vert magnitude^2 + horiz magnitude^2). 2) If a ball is rolled down an incline of 30 degrees. We can find the ds or if we change the eqn a little bit, we can find the vf by the eqn: magnitude=sqrt(vert magnitude^2 + horiz magnitude^2). 3) If a ball is thrown down a building with a horizontal and vertical velocity we can find the angle the ball will travel by using the eqn: arctan(vertical v0/horizontal v0).
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09:40:33 ** 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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