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Why are bearings calculated using velocity in postion vectors?

Hey guys I was doing some furthers kinematics question and I realized all the bearing questions were worked out using the velocity position vector why not the position or displacement vector instead?
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Euler7
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Because vectors are useful in displaying directions and plus you can work out the magnitude of velocity from the vector anyway
Original post by Stormragexox
Hey guys I was doing some furthers kinematics question and I realized all the bearing questions were worked out using the velocity position vector why not the position or displacement vector instead?


We can write the position vector of a moving particle as
s = s1 + vt

where s1 is initial position, v is the velocity

this is similar/equivalent to a vector line equation, where vector v is the direction vector.
Original post by Stormragexox
Hey guys I was doing some furthers kinematics question and I realized all the bearing questions were worked out using the velocity position vector why not the position or displacement vector instead?

If you want the direction something is moving in, you're going to want to use the velocity. If you want the direction something actually is (relative to some other point) you'll want to use a displacement vector.

In other words, there are absolutely cases (not necessarily covered in your course) where you will want to use velocity, and cases where you want to use displacement.

As to why you're only seeing questions involving velocity: it's hard to know without seeing the questions/syllabus. But if you're talking about motion (i.e. kinematics), then questions where you consider the bearing of the displacement vector tend to be quite hard (unless the bearing doesn't change) and so beyond A-level. Whereas there are lots of relatively easy questions you can ask about how bearings relate to relative velocity, closest possible approach of two ships, etc.

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