g=Gravitational Field Strength (modeled as 10m/s^2)
Assume lack of air resistance
A particle, 35 metres off of the ground, is projected upwards, and takes 4 seconds to fall to the ground.
The acceleration should therefore be -10, the total net displacement during that time should be -35, and the time is obviously 4 seconds.
Since s=vt - 1/2 at^2
-35=4v - 1/2*-10*4^2
However, according to my teacher, s is positive. I cannot comprehend this, since a is stated to be negative, and it is accelerating towards the ground, and s is a vector in the same direction as the acceleration.
His answer was something along the lines of s being the 'starting value'. Can anyone explain this to me?
EDIT: I put 10 instead of -10 for a