17querry

course phy201

assignment #019

019. `query 19

Physics I

04-15-2008

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20:01:44

Query class notes #20

Explain how we calculate the components of a vector given its magnitude and its angle with the positive x axis.

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RESPONSE -->

by taking the cosign of the angle

confidence assessment: 1

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20:02:57

** STUDENT RESPONSE:

x component of the vector = magnitude * cos of the angle

y component of the vector = magnitude * sin of the angle

To get the magnitude and angle from components:

angle = arctan( y component / x component ); if the x component is less than 0 than we add 180 deg to the solution

To get the magnitude we take the `sqrt of ( x component^2 + y component^2) **

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RESPONSE -->

you got to multiply the magnitude to the cosign of the angle

self critique assessment: 3

It should be clear from the given solution that you use the cosine fo the x component and the sine for the y component.

Your self-critique should have acknowledged this.

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20:11:26

Explain how we can calculate the magnitude and direction of the velocity of a projectile at a given point.

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RESPONSE -->

confidence assessment: 0

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20:12:50

** Using initial conditions and the equations of motion we can determine the x and y velocities vx and vy at a given point, using the usual procedures for projectiles.

The magnitude of the velocity is sqrt(vx^2 + vy^2) and the angle with the pos x axis is arctan(vy / vx), plus 180 deg if x is negative. **

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RESPONSE -->

self critique assessment: 1

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20:14:23

Explain how we can calculate the initial velocities of a projectile in the horizontal and vertical directions given the magnitude and direction of the initial velocity.

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RESPONSE -->

magnitude divided by the sin of direction of the projectile

confidence assessment: 0

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See my notes on this and on previous assignments related to self-critique. You are as always welcome to submit a copy of any of these documents with inserted questions and/or self-critiques, designated by &&&&.