Part A - when thrown upwards why do we take the acceleration as positive?

[dire drum]

And then why do we take the acceleration when it comes downwards as negative?

cuz it moves freely under gravity right

so surely we should take downwards as positive acceleration aka 9.8

The MS says this and I don’t get why A is negative

[viral scarab]

You can choose which direction you want to take as the positive direction

But the acceleration and velocity are in opposite directions so will have opposite signs

[dire drum]

I chose the downwards as the positive direction for acceleration cuz it says it moves freely under gravity

[viral scarab]

Idk why ur thinking that statement is significant

It just means the only force acting on it is the one from gravity

So if you choose down as positive the s= 0, u=-14.7, v = 14.7, a = 9.8

[dire drum]

bc in the question it says the stone is moving freely under gravity downwards

[dire drum]

wait what

I’m so confused now

How come we swap the signs with A and the U and V, I don’t think I was taught this imo

[viral scarab]

….. if down is positive then up is negative…..

[dire drum]

oh yeah

forgot abt that mb 😭

ohhhh, right that makes sense now 😭

wait why

What topic is this called in mechanics

[true sand]

constant acceleration and SUVAT equations?