- 119

- 0

## Main Question or Discussion Point

hey guys,

i studied "applied maths" in "high school" [the irish version!!]

we studied projectile motion and velocity vectors etc,

we worked on the premise that gravity affects only the verticle velocity of the projectile

so that:

for a projectile given an initial velcoity both horizontally and vertically (i and j)

the horizontal component would remain unchanged [obviously diregarding any frictional forces], while the verticle component is subject to change due to gravity.

fine.

now i turn my mind to a pendulum, free to swing both left and right, as well as front to back, and i figure: the left-right motion can be treated seperatly to the front-back motion, each discribing, in that direction,the motion it would otherwise assume were the other direction neglected. and then:

i think surely not!

> i imagine that, in the left-right motion the pendulum is swinging not as a pendulum but rather in full circuls, and very fast. i then reason (rightly or wrongly) that were i to nudge the pendulum in the forward-backward direction that it would not oscillate forwards and backwards but rather be restored to its inital position. similar to the way that a bullet which spins along the axis of its trajectory will not become unstable.

assuming that what i have said is correct [open to correction!] i am left with a conumdrum:

when is it acceptable to split an objects motion into x,y or x,y,z and why

is it something to do with rotation?

or am i missing something else more fundamental.

thanks for your thoughts!

james

i studied "applied maths" in "high school" [the irish version!!]

we studied projectile motion and velocity vectors etc,

we worked on the premise that gravity affects only the verticle velocity of the projectile

so that:

for a projectile given an initial velcoity both horizontally and vertically (i and j)

the horizontal component would remain unchanged [obviously diregarding any frictional forces], while the verticle component is subject to change due to gravity.

fine.

now i turn my mind to a pendulum, free to swing both left and right, as well as front to back, and i figure: the left-right motion can be treated seperatly to the front-back motion, each discribing, in that direction,the motion it would otherwise assume were the other direction neglected. and then:

i think surely not!

> i imagine that, in the left-right motion the pendulum is swinging not as a pendulum but rather in full circuls, and very fast. i then reason (rightly or wrongly) that were i to nudge the pendulum in the forward-backward direction that it would not oscillate forwards and backwards but rather be restored to its inital position. similar to the way that a bullet which spins along the axis of its trajectory will not become unstable.

assuming that what i have said is correct [open to correction!] i am left with a conumdrum:

when is it acceptable to split an objects motion into x,y or x,y,z and why

is it something to do with rotation?

or am i missing something else more fundamental.

thanks for your thoughts!

james