OpenQuery21

course PHY 121

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021. `query 21*********************************************

Question: `q 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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Your solution: To find the final speed and direction of motion of a projectile, if we know the horizontal velocity and `ds: the vertical a is always 9.8m/s^2, and the horizontal velocity won’t change. Once we find the final velocity using `ds in the appropriate equation, we can use angle = arctan (vy/vx) to find the direction.

confidence rating:

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Given Solution: ** 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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Self-critique (if necessary): I’m starting to get confused the more things we keep applying the artcan/cos/sin/pythag stuff to. Like, if you tell me “I go this way, you go that, what’s the combined,” I get it, but I have trouble otherwise picking out problems where I can use these concepts.

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Self-critique Rating:

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Question: `qGive 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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Your solution: If two objects collide we have to look at the magnitude of each of them and the resulting direction or velocity or Force “transferred”, or if something rolls off a ramp at an angle to hit the floor, it will have a horizontal and vertical velocity that combine at an angle to bring the ball to strike the ground. Another example would be if a force is acting on an object on a ramp so that the “pressure” is being applied at an angle, where we would have to use a skewed axis to analyze the magnitude and direction.

confidence rating:

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Given Solution: ** GOOD STUDENT RESPONSE:

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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Self-critique (if necessary): OK

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Self-critique Rating:

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&#This looks very good. Let me know if you have any questions. &#