You are Here: Home >< Maths

# M2

Announcements Posted on
TSR's new app is coming! Sign up here to try it first >> 17-10-2016
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!

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: April 6, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Today on TSR

### How does exam reform affect you?

From GCSE to A level, it's all changing

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read here first

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams