Query Assignment 21

course phy 201

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Physics I

07-19-2007

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00:00:25

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 -->

horizontal component is equal to the initial velocity

vertical velocity is 0 and its acceleration is 9.8 m/s/s

we can find the final velocity with the equation

vf^2= v0^2 + 2 a `ds

the speed is the magnitude and is found using the pythagorean theorm and the direction is found using the arctan (y/x)

the components are

Vx= V * cos (theta)

Vy= V * sin (theta)

x is horizontal and y is vertical

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00:00:48

** 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 -->

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.

I completely understand this

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00:03:22

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 -->

An object falling and finding the velocity and acceleration

momentum and force are vector quantities

displacement is also a vector quanity- this is how far the object moves

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00:04:29

** 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 -->

I understand that i should have used actual examples, but i didnt understand how to use the examples for the vector quanitities

I also understand that the vector components are the horizontal and vertical components that produce the same effect as the examples

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Good responses. Let me know if you have questions. &#