Vector problem

[cosmic]

Hi guys,

Back again with another problem which I'm sure you'll enjoy!


These are my answers:

a) p=340 km h^-1i-588.9 km h^-1j and w=53.6 km h^-1i+45 km h^-1j.

b) v=286.4 km h^-1i-633.9 km h^-1j.

c) Magnitude of v=696 km h^-1 (to the nearest km h^-1) and the direction of the velocity v=294° (to the nearest degree).

I'm not sure whether they are correct so would really appreciate if someone could check them to see whether or they are right.

Thanks

 

[cosmic]

Anyone?

 

[srmichael]

Hi guys,

Back again with another problem which I'm sure you'll enjoy!



These are my answers:

a) p=340 km h^-1i-588.9 km h^-1j and w=53.6 km h^-1i+45 km h^-1j.

b) v=286.4 km h^-1i-633.9 km h^-1j.

c) Magnitude of v=696 km h^-1 (to the nearest km h^-1) and the direction of the velocity v=294° (to the nearest degree).

I'm not sure whether they are correct so would really appreciate if someone could check them to see whether or they are right.

Thanks

I got a different wind vector and as a result, all the following calculations are different. Check your work. One hint: a 220º bearing is in the third quadrant and your wind vector puts it in the first quadrant.

 

[cosmic]

I got a different wind vector and as a result, all the following calculations are different. Check your work. One hint: a 220º bearing is in the third quadrant and your wind vector puts it in the first quadrant.

Hi,

Thank you for your reply. I understand that the wind vector is a third quadrant angle but the question says that the wind is blowing from a bearing of 220º so that suggests that it's moving in the opposite direction. For instance a southerly wind blows towards the north. With that in mind can you confirm whether you get similar answers.

Thanks.

 

[srmichael]

Hi,

Thank you for your reply. I understand that the wind vector is a third quadrant angle but the question says that the wind is blowing from a bearing of 220º so that suggests that it's moving in the opposite direction. For instance a southerly wind blows towards the north. With that in mind can you confirm whether you get similar answers.

Thanks.

Ah! I did not even see that. Yes, that changes things, however I still get a different wind vector. Maybe you switched sine and cosine in your calc

 

[cosmic]

Ah! I did not even see that. Yes, that changes things, however I still get a different wind vector. Maybe you switched sine and cosine in your calc

I've made a few changes to the calculations, so I get

p = -588.9i + 340j
w= 53.6i + 45j

therefore the resultant v becomes,

v= -535.3i + 385j

Finally I get the magnitude 659.4 km h^-1 and the bearing 144.3 degree.

I know the wind vector is still the same this question is driving me nuts . Any help would be greatly appreciated.

Thanks.

 

[srmichael]

I've made a few changes to the calculations, so I get

p = -588.9i + 340j
w= 53.6i + 45j

therefore the resultant v becomes,

v= -535.3i + 385j

Finally I get the magnitude 659.4 km h^-1 and the bearing 144.3 degree.

I know the wind vector is still the same this question is driving me nuts . Any help would be greatly appreciated.

Thanks.

I got the same magnitude and bearing, though the vectors you have are reversed from what they should be. They should be:

p = 340i - 588.9j
w= 45i + 53.6j

therefore the resultant v becomes,

v= 385i - 535.3j

 

[cosmic]

I got the same magnitude and bearing, though the vectors you have are reversed from what they should be. They should be:

p = 340i - 588.9j
w= 45i + 53.6j

therefore the resultant v becomes,

v= 385i - 535.3j

Did you take into consideration the fact in the question that states "take i to point east and j to point north"?

 

[srmichael]

Did you take into consideration the fact in the question that states "take i to point east and j to point north"?

Yes. This is the typical unit vector notation. i for the x (east/west) direction and j for the (north/south) direction.

Remember, the vector component form is <magnitude*cos(Θ), magnitude*sin(Θ)>

 

[cosmic]

Yes. This is the typical unit vector notation. i for the x (east/west) direction and j for the (north/south) direction.

Remember, the vector component form is <magnitude*cos(Θ), magnitude*sin(Θ)>

Oh I see that's cleared it up.

Thank you so much.