When solving projectile motion question (1 Viewer)

[gahyunkk]

If question gives us a value of velocity & angle such as v=20m/s and angle=30,
can we put these values in at the first place when we are finding initial components and equation of x&y? Or is it better to still work out with V and alpha, then sub in the values at the end?

 

[aDimitri]

I usually substitute it in at the start, but if the question says "...The angle of elevation now changes..." or "...The starting velocity now changes..." in a later part, you'd be better off to have done it with V & alpha. I never do it that way simply because i feel like it's just a memorized page from a textbook rather than actually deriving it for the specific situation, but mark wise it shouldn't matter at all.

 

[gahyunkk]

I usually substitute it in at the start, but if the question says "...The angle of elevation now changes..." or "...The starting velocity now changes..." in a later part, you'd be better off to have done it with V & alpha. I never do it that way simply because i feel like it's just a memorized page from a textbook rather than actually deriving it for the specific situation, but mark wise it shouldn't matter at all.

Yea i prefer to sub them in at the beginning but i was just wondering coz some of the solutions put the values at the end

 

[Carrotsticks]

I do it at the start, keeps things cleaner overall

 

[gahyunkk]

I do it at the start, keeps things cleaner overall

Yeap same [emoji106]

 

[emilios]

I do it at the start, keeps things cleaner overall

If they give you clean numbers. Any surds or fractions then see ya later mate.

So yeah, personal preference but I like working with symbols up until the end, which is how I believe higher level physics generally is too (oh lord the amount of constants in pysics). Also, my teacher is a massive pain in the ass and will always give us really shitty numbers to use e.g. find the equation of the tangent to the this ellipse at the point [8sqrt(7)/2 , 2sqrt(3)]. He thinks he's making the test harder/ more challenging when really it's the cheapest way to go about it /rant over.