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few questions about newton's 2nd law that i'm stuck on =[ Watch

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    An 80kg skier has a force 200N exerted on him down a slope.
    Calculate his aceleration down the slope.
    Is the slope less than or more than 45(degrees)? explain your answer.


    80 x 9.81 = 784.8N

    I'm not sure which one of these is right...

    200N = 80 x a
    a = 2.5 m/s^2

    or

    200 - 784.8/cos (theta) = 80 x a

    a=16000-62784/cos (theta)


    I'm not sure how to work out the second part.



    Thanks!!
    any help will be greatly appreciated!
    and +rep to the person who offers the most thorough and conclusive answer!
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    200N = 80 x a
    a = 2.5 m/s^2

    thats right

    well it says 'explain' so no calculation generally needed...so my guess would be more but i dont have a proper answer to that....just cant imagine someone whose 80kgs going down a slope at 2.5ms-1 at an angle less than 45
    sorry thts all i can do atm
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    (Original post by Spongebob*No*Pants)
    An 80kg skier has a force 200N exerted on him down a slope.
    Calculate his aceleration down the slope.
    Is the slope less than or more than 45(degrees)? explain your answer.


    80 x 9.81 = 784.8N

    I'm not sure which one of these is right...

    200N = 80 x a
    a = 2.5 m/s^2

    or

    200 - 784.8/cos (theta) = 80 x a

    a=16000-62784/cos (theta)


    I'm not sure how to work out the second part.



    Thanks!!
    any help will be greatly appreciated!
    and +rep to the person who offers the most thorough and conclusive answer!

    Well you've worked out the acceleration, a = 2.5 m/s^2.

    And if you think about a block sliding down a slope, the acceleration of the block is a = g \sin \theta if the angle of the slope is theta.

    so the angle of this slope is:  \frac{2.5}{9.8} = \sin \theta

    which is less than 0.7 (which sin 45 approximately equals), so the slope is less than 45 degrees.
 
 
 
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