AQA M1 Jan 2012 Q6

AQA Mechanics 1 exam paper on constant acceleration, inclined slope and Newton's second law. Using SUVAT equations

[mathedup]

Hi Charlie.. I understand your confusion and what you are saying is a common misconception that many students have. Our resultant force (58.8N) is acting parallel to the plane. This is the direction we want to resolve in..

Our weight (70g) is acting directly down. We can resolve this weight into 2 components; parallel to the plane, and perpendicular to the plane. In the red forces triangle I have drawn, I have shown that the weight would be the hypotenuese...

[mathedup]

...the perpendicular would be adjacent to the alpha and the parallel component would be opposite the alpha.
The confusion you are having is you are seeing the slope as the right angle triangle with the plane being the hypotenuse side but this is not the case..

[ZombieTubeu]

for part ci why do we use g and not the acceleration we have previously just found in the answer ?!

[charlie]

Part ci)... HOW?!
You have - 58.8=70gsin(alpha)
SURELY its 58.8sin(alpha)=70g
Can't work this out...