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    http://www.mei.org.uk/alevelpapers#M2
    For the June 2005 M2 paper, for q2iv, in the examiners report it says
    A sizeable number of candidates ignored the method requested in the questionand attempted a solution using Newton’s second law and the constantacceleration equations, obviously not appreciating that if both the power and theresistance are constant, the acceleration cannot be.

    I don't get why if both the power and the resistance are constant, the acceleration cannot be.
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    Quick hint: P = Fv yet power is constant, and velocity varies, so F must vary alongside velocity to keep power constant. Hence you have one variable force when resolving and a bunch of constant forces that can't cancel a variable force so the resultant force is variable too, and hence so is acceleration.
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    (Original post by runny4)
    http://www.mei.org.uk/alevelpapers#M2
    For the June 2005 M2 paper, for q2iv, in the examiners report it says
    A sizeable number of candidates ignored the method requested in the questionand attempted a solution using Newton’s second law and the constantacceleration equations, obviously not appreciating that if both the power and theresistance are constant, the acceleration cannot be.

    I don't get why if both the power and the resistance are constant, the acceleration cannot be.

    Forgot to quote you, see above.
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    (Original post by runny4)
    http://www.mei.org.uk/alevelpapers#M2
    For the June 2005 M2 paper, for q2iv, in the examiners report it says
    A sizeable number of candidates ignored the method requested in the questionand attempted a solution using Newton’s second law and the constantacceleration equations, obviously not appreciating that if both the power and theresistance are constant, the acceleration cannot be.

    I don't get why if both the power and the resistance are constant, the acceleration cannot be.
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    If you have P=F_{drive}v and R=F_{res} constant, then \frac{P}{v}-R=ma.
    Since P and R are constant, the only way you can have constant acceleration is if v is itself constant, meaning that a=0.
    However in your case v is not constant, and so a is not constant.
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    (Original post by Zacken)
    Quick hint: P = Fv yet power is constant, and velocity varies, so F must vary alongside velocity to keep power constant. Hence you have one variable force when resolving and a bunch of constant forces that can't cancel a variable force so the resultant force is variable too, and hence so is acceleration.
    thank you
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    (Original post by runny4)
    thank you
    You're welcome!
 
 
 
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