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<a https://www.thestudentroom.co.uk/showthread.php?t=7467335'> Year 12s: what will be the first way you research your future options? >>
<a https://www.thestudentroom.co.uk/showthread.php?t=7467335'> Year 12s: what will be the first way you research your future options? >>
<a https://www.thestudentroom.co.uk/showthread.php?t=7467335'> Year 12s: what will be the first way you research your future options? >>

M2

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.
Reply 1
Avatar for Zacken
Zacken
22
Quick hint: P=FvP = 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.
Reply 2
Avatar for Zacken
Zacken
22
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.
Reply 3
Avatar for joostan
joostan
13
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.

Spoiler

(edited 8 years ago)
Reply 4
Avatar for runny4
runny4
OP
6
Original post by Zacken
Quick hint: P=FvP = 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
Reply 5
Avatar for Zacken
Zacken
22
Original post by runny4
thank you


You're welcome!

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