Can someone clarify some things for me?

  • Thread starter Thread starter matt@USA
  • Start date Start date
AI Thread Summary
The discussion focuses on clarifying the definitions of variables in 2D motion equations, particularly x, y, V, and Vnaught. X and y represent positions along their respective axes, determined by the user. V denotes the velocity of an object, while Vnaught signifies the initial velocity at time t=0. The conversation also emphasizes the use of subscripts to differentiate components in vector equations. The example provided illustrates how to calculate the final velocity of an object in free fall using the appropriate kinematic equation.
matt@USA
Messages
25
Reaction score
0
I don't know if I am just looking too much into the problems or what, but I am having a very hard time determining what is what in the problems. I am not confident on what I pick as Vnaught, V, x, y, etc ... Will someone please help?
I will tell you how I determine it, and you can correct me.

x=where it lies on the x axis?
y=where it lies on the y axis? ... Both of these are determined by me? Correct?

So is V the velocity of the object? And what is Vnaught?

These are all pertaining to 2D equations.
 
Physics news on Phys.org
Naught is usually the initial value of something. If you have a position graph then you could say that x naught is the starting position of the object. You see subscripts used a great deal. i usually denotes an initial value as well, f usually means the final value. Aside from that everything else is pretty descriptive. When you are dealing with 2+d problems, you might see subscripts of x and y to let you know which component it is. Say you have a vector r, they might say that a_{rx} is the acceleration of the x component of the r vector and so on.
 
Last edited:
Yes, x and y are positions, measured along their respective coordinate axes.

v is velocity. In general it varies with time (i.e., pick a time t, and you'll get a specific value for v).

v0 is initial velocity (i.e. velocity at t = 0).
 
So what is V?
 
matt@USA said:
So what is V?

In the context you have provided, V would be the velocity at the time to are dealing with.

Vo is the initial velocity. V is the velocity later.

eg: you might want to know "if a stone is thrown vertically down from the top of a 30m tower with a velocity of 2 ms-1, how fast will it be traveling just before it hits the ground -[take g=10].

everything is happening downwards, so let down be positive.

Vo = 2.0
a = 10
x = 30
V = ??

Best formula to use would be

V2 = Vo2 + 2as

V2 = 4 + 2x10x30 = 604

so V = 24.6
 
I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
Thread 'A cylinder connected to a hanging mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top