Physics questions

[TrueTears]

yeah i suck shit at physics and i gotta read like 1000 pages in a week, so i am skim reading my ass off, pls help with my noob questions, any assistance wud be appreciated

http://img388.imageshack.us/i/physics1.jpg/

so why the hell is the velocity vector pointing left? i have no clue

can someone please explain? and by explain i mean try not to leave out any steps coz i seriously suck at this.

thanks again <3

[kamil9876]

It's showing an object moving from right to left (decreasing its x value), with decreasing SPEED. But this is INCREASING velocity. Since dx/dt is really increasing.

[TrueTears]

sorry i only get the moving from right to left part, becoz v_x is negative, i dont get anything else u said

[superflya]

i fail but i think his trying to say velocitys increasing as the displacement increases.

[kamil9876]

I'm talking about the second pic btw (since it's the one that has v pointing left)

It's basically a case of, consider this sequence:

-10,-9,-8,-7...

The numbers are getting "smaller" but they are "increasing".

Likewise here the velocity is negative and increasing but the absolute value (which is the speed, which is represented by the LENGTH of the vector) is decreasing.

[qshyrn]

yeah i suck shit at physics and i gotta read like 1000 pages in a week, so i am skim reading my ass off, pls help with my noob questions, any assistance wud be appreciated

http://img388.imageshack.us/i/physics1.jpg/

so why the hell is the velocity vector pointing left? i have no clue

can someone please explain? and by explain i mean try not to leave out any steps coz i seriously suck at this.

thanks again <3

the velocity vector is going to the left because THE OBJECT IS MOVING AND HAS A VELOCITY IN THAT DIRECTION, and the arrows are shortening because the acceleration is in the opposite direction

[rashmi_34]

if the vector value of acceleration is in the opposite direction of the velocity vector (i.e. v=positive number, a=negative number or vice versa) it means that the object is de-accelerating, i.e. slowing down (eg a car coming to halt at the traffic lights).

[TrueTears]

oh thanks guys i get it, more questions coming soon

[TrueTears]

what does v_fs, v_is and all those subscript mean??

[brightsky]

This might help.

http://en.wikipedia.org/wiki/Equations_of_motion#Equations_of_uniformly_accelerated_linear_motion

EDIT: For , the book already defined it on the left as "final velocity".

[TrueTears]

still dont get it, what is v_fs? what the hell is s???

explain plsss im dumb at physux

[TrueTears]

how do u do this Q? what is a trajectory?

[superflya]

isnt the trajectory the path..

[TrueTears]

probs, how do u do the q? =S

[/0]

hmmm, well, let's take the usual cartesian axes

for the first three seconds you would just draw it going straight up, with



(from )

Then for you will have a pair of parametric equations:

and

Which you can solve for in terms of to sketch the path.