A second opinion on a Neap 2011 exam

[My name aint bob]

Hey, i might just throw one more question at you guys, regarding Q2 of motion, in Neap 2011.

2kg remote control car, under constant driving force aceelerates from rest and reaches a constant speed after travelling 5m in a straight line. there is also a graph of Frictional force vs Distance, witch levels off at point (5m, 20N) (so that frictional force is from then on constant at 20N)

Q. Calculate the speed of the car when it has travelled 5m

the answer given did: change in KE= work done on car – work done to overcome friction, and then found the area under the graph. and approached it that way.

However i did v^2= u^2 + 2ax, and found an average of acceleration by adding 10 and zero and deviding by two (10 becouse at 0m, a=F(net)/mass =20-2)

Hopefully this hasn't come out massively confusing, does anyone know if this is a valid approach

[max payne]

That's what I did!!!
And I thought that was more accurate then their approach to be honest. I think it was still within one decimal point from their answer so you should still get the mark

[My name aint bob]

yeah i thought so aswell. I was off by .5, so i just took off one mark for the hell of it

anyways im glad im not the only one,  i think its more accurate as-well.