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Homework Help: Phys/trig Q?s why are they wrong

  1. Oct 3, 2005 #1
    1. [SFHS99 3.P.23.] A submarine dives 100.0 m at an angle of 10.0° below the horizontal. What are the horizontal and vertical components of the submarine's displacement? (Assume that upward and the direction of the submarine's horizontal motion are positive.)

    what i got

    _98.48_m (horizontal) << correct
    _17.36_ m (vertical) << wrong?

    3. [SFHS99 3.P.26.] A person walks 21.0° north of east for 3.50 km. How far would another person walk due north and due east to arrive at the same location?
    ____?____km north
    __1.25___ km east <wrong

    4. [SFHS99 3.P.27.] A roller coaster travels 35.1 m at an angle of 44.0° above the horizontal.

    How far does it move horizontally?
    ___24.4___ m <wrong
    How far doe it move vertically?

    thanks i have been using Soh Cah Toa for the trig stuff so i ithnk itts right if im missing a step plaese explain thanks alot
  2. jcsd
  3. Oct 3, 2005 #2


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    Science Advisor
    Homework Helper

    On number one, the angle is 10 degrees below the horizontal. That means your vertical component is negative.

    On the other two, try drawing the problem out on paper. You're mixing up your components.

    For example, the second problem is 21 degrees north of east. You solved for 21 degrees east of north.

    In other words, you probably have the trig part down, but you need to work on defining the problem you're trying to solve.
    Last edited: Oct 3, 2005
  4. Oct 3, 2005 #3
    What you are calculating (the x displacemnt and y displacement) is called component vector sum or resolving the vector into its components. For the X or horizontal component use [Vx = V cos theta] and for the y or vertical component use [Vy = V sin theta].
    Note: North is +y, south is -y, east is +x, west is -x
    Use Polar Angles for all problems.
    make sure you get the +direction and - direction correct

    Answers (rectangular coordinates):
    1. (+98.48 -17.36)
    2. (3.26 E, 1.25 N)
    3. (+25.25, +24.38)
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