Kinematics: given 2 position vectors, time, and V of earlier

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Given two position vectors, the change in time, and the initial velocity of a particle, one can calculate average velocity and displacement. Average velocity is derived from displacement divided by the change in time, while displacement can be determined directly from the position vectors. The discussion highlights that while average acceleration and final velocity can be calculated under certain conditions, they are not universally applicable without additional information. Specifically, the relationship for final velocity relies on the assumption of constant acceleration. Thus, the key quantities that can be reliably calculated are average velocity and displacement.
Dillon Keeler
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If you know the position vectors of a particle at two points along its path, change in time between the two positions, and the particle's velocity at the earlier point, what quantities can you calculate?

a)average acceleration
b)final velocity
c)average velocity
d)displacement

My answer was all of the above because one can find
d) by just the two position vectors
c) by ( displacement / change in time )
b) by Vaverage= (1/2)(Vinitail+Vfinal)
a) by average acceleration = ( change in velocity / change in time)

however the answer is just c) and d). Am I forgetting to take something in consideration?
 
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Your "b" is true only for a special case. It is not a generally valid relationship.
Do you know what is this special case? What is the condition to have this relationship?
 
nasu said:
Your "b" is true only for a special case. It is not a generally valid relationship.
Do you know what is this special case? What is the condition to have this relationship?
Constant Acceleration?
 

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