Two dimensional kinematics

  • Thread starter indietro
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Homework Statement


a flying saucer manueverign with a constant acceleration is observed with the positions and velocities shown below. what is the saucer's acceleration?

Homework Equations


a = [tex]\Delta[/tex]v / t

The Attempt at a Solution


so a time is not given.. is there another way to find acceleration?
** actually if someone knows a site that gives a clear and concise tutorial on two-dimensional kinematics that would be great :). I know there is one attached to this site.. but i do better with actual examples and more visual.
 

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  • #2
tiny-tim
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a flying saucer manueverign with a constant acceleration is observed with the positions and velocities shown below. what is the saucer's acceleration?

so a time is not given.. is there another way to find acceleration?
Hi indietro! :smile:

(I can't see the picture yet, but …)

The standard trick for finding dv/dt from v and s without involving t is to use the chain rule …

dv/dt = dv/dx dx/dt = v dv/dx :wink:
 
  • #3
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oo ok for the picture it is a x-y graph that shows a point at (0.0) with a vertical vector (200[tex]\hat{j}[/tex] m/s) and a second point at (2000, 1000) with a south-east vector (200[tex]\hat{i}[/tex] - 100[tex]\hat{j}[/tex] m/s)

for the chain rule: is the v the final velocity?
 
  • #4
tiny-tim
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v = dx/dt
 
  • #5
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so i have a question: for an x-y graph showing the trajectory, what does [tex]\vec{r}[/tex] (starts at origin and goes to a point on the trajectory) tell me? the velocity at that point? or does it only tell me the direction of velocity at that point?
 
  • #6
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sorry but im really confused as how to relate an xy-graph, a vx graph, a vy graph and acceleration. Like what does each tell me, how can i find position after a certain time, how can i find acceleration?
 
  • #7
tiny-tim
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Hi indietro! :smile:

(just got up :zzz: …)
so i have a question: for an x-y graph showing the trajectory, what does [tex]\vec{r}[/tex] (starts at origin and goes to a point on the trajectory) tell me? the velocity at that point? or does it only tell me the direction of velocity at that point?
r only tells you the position, and the direction of the tangent of the trajectory tells you the direction of the velocity.
sorry but im really confused as how to relate an xy-graph, a vx graph, a vy graph and acceleration. Like what does each tell me, how can i find position after a certain time, how can i find acceleration?
Why are you using a graph? Does the question tell you to?

If it doesn't, then forget graphs, and just use equations. :smile:
 
  • #8
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yes the question gives me all the information in the form of an vx graph and vy graph ...:(
 
  • #9
tiny-tim
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yes the question gives me all the information in the form of an vx graph and vy graph ...:(
hmm … I still can't see your picture.

I'll have to wait until I can see it.

(I've reported it, so hopefully it'll come up soon :redface:)
 
  • #10
tiny-tim
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oooh, I see it now! :tongue2:​

ok, that isn't a graph (a graph would be a continuous curve) …

it's just a diagram, defining the two velocities in a picture instead of in words.

So you don't have to use a "graph method" …

just write the velocities as 200j and 200i - 100j, and carry on from there. :smile:
 

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