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# M2 watch

1. 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.
2. Quick hint: 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.
3. (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.
4. (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:
Show
If you have and constant, then .
Since and are constant, the only way you can have constant acceleration is if is itself constant, meaning that .
However in your case is not constant, and so is not constant.
5. (Original post by Zacken)
Quick hint: 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
6. (Original post by runny4)
thank you
You're welcome!

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