Finding Acceleration in Two-Dimensional Kinematics

[indietro]

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 = $$\Delta$$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.

 

[tiny-tim]

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!

(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

 

[indietro]

oo ok for the picture it is a x-y graph that shows a point at (0.0) with a vertical vector (200$$\hat{j}$$ m/s) and a second point at (2000, 1000) with a south-east vector (200$$\hat{i}$$ - 100$$\hat{j}$$ m/s)

for the chain rule: is the v the final velocity?

 

[tiny-tim]

v = dx/dt

 

[indietro]

so i have a question: for an x-y graph showing the trajectory, what does $$\vec{r}$$ (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?

 

[indietro]

sorry but I am 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?

 

[tiny-tim]

Hi indietro!

(just got up :zzz: …)

so i have a question: for an x-y graph showing the trajectory, what does $$\vec{r}$$ (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 I am 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.

 

[indietro]

yes the question gives me all the information in the form of an vx graph and vy graph ...:(

 

[tiny-tim]

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 )

 

[tiny-tim]

oooh, I see it now! ​

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.