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January 25, 2015

January 25, 2015

Posted by **mo** on Sunday, January 22, 2012 at 9:51am.

find (a) the x and y components of the plane’s average acceleration and (b) the magnitude and direction of its average acceleration

d) for this time interval, find the direction of its average acceleration?

=? counterclockwise from + x axis

im having a hard time solving this problem

and for question (a) fo x i got 104.8 i got that wrong plus i even rounded it to 150 still wroung

- Physics -
**drwls**, Sunday, January 22, 2012 at 10:03amvx1 = 695 km/h = 193.06 m/s

vy1 = 440 km/h = 122.22 m/s

vx2 = 933 km/h = 259.17 m/s

vy2 = 465 km/h = 129.17 m/s

avarage ax = (vx2 - vx1)/7.12 s

= 9.29 m/s^2

average ay = (vy2 - vy1)/7.12s

= 0.98 m/s^2

I hope you can see where you made your error and proceed from there.

- Physics -
**mo**, Sunday, January 22, 2012 at 10:10ambut it has to equal km/h^2 and i got those anwsers wrong

- Physics -
**drwls**, Sunday, January 22, 2012 at 10:18amI am surprised they are asking for acceleration in unconventional units of km/h^2. You should recheck that.

If you want km/h^2 units, the time interval is

7.12 s = 1.978*10^-3 h

ax = (933-695)/1.9878*10^-3

= 3.02*10^4 km/h^2

so I still don't see how you got your answer of 104.8 in whatever units you are using

- Physics -
**mo**, Sunday, January 22, 2012 at 10:25am(933-695)/7.12- 4.85 = 238/2.27= 104.84 thats how i got that anwser...

- Physics -
**drwls**, Sunday, January 22, 2012 at 10:37amYou are quite right, I forgot to do the time subtraction for the interval. I also made a computational error in the division.

7.12 - 4.85 = 2.27 s = 6.306*10^-4 h

ax = 29.1 m/s^2

= 3.77*10^5 km/h^2

Here is what you did wrong:

To get acceleration in units of km/h^2, you divided the speed change in km/h by the time interval in SECONDS.

What you did gave you the average acceleration in (km per hour) per second

- Physics -
**mo**, Sunday, January 22, 2012 at 10:46amhow did you get 29.1 to = 3.77* 10^5?

- Physics -
**mo**, Sunday, January 22, 2012 at 11:00amnevermind you converted it

- Physics -
**mo**, Sunday, January 22, 2012 at 11:41amb i got 3.96x10^4 km.h and i already did the magnitude which it 3.80x10^5

for the last question about the "for this time interval, find the direction of its average acceleration.

= ? countercloclock wise from + x axis

- Physics -
**drwls**, Sunday, January 22, 2012 at 12:21pmThe direction of the avg. acceleration, clockwise from +x axis, is arctan ay/ax

You have the wrong dimensions following your ax. km.h is not a dimension of acceleration.

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