# Vectors: Average Velocity, Acceleration, Speed

1. Sep 3, 2014

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1. The problem statement, all variables and given/known data

A car is moving with speed $17.4m/s$ due south at one moment and $28.3m/s$ due east $7.50s$ later.

A. Determine the magnitude and direction of its average velocity over this time interval.
B. Determine the magnitude and direction of its average acceleration over this time interval.
C. What is its average speed over this time interval?

The attempt at a solution

I'm not at all sure that there's enough information here to determine any of these. From the information given, would be it wise to assume that the car had been traveling at $17.4m/s$ due south for a period of $7.50s$ and then switched velocities at $t=7.50s$, or should I assume that at some point within those $7.50s$ the car's velocity changed (perhaps gradually), and $28.3m/s$ due east is its final recorded instantaneous velocity?

I'm assuming that if I can find the magnitudes for the $x$ and $y$ components (or in this case, South and East components) I can solve most, if not all of the questions, but what are $Vx$ and $Vy$? How does the time factor into this?

Thank you,

2. Sep 3, 2014

### ehild

I think the problem means that the velocity is 17.4m/s due South at time t1=0 and it is 28.3m/s due East at t2=7.5 s.

I do not think you can answer A and C, keeping in mind the definition of average velocity and speed. Check if you read the whole problem.

You can consider East as X direction, and South as y directions, and the velocities as vectors. How is acceleration defined?

ehild

3. Sep 3, 2014

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Thank you, ehild.

You were correct in stating that A and C cannot be solved, and I was able to compute the average acceleration by breaking the vectors into their components.

4. Sep 3, 2014

### Staff: Mentor

Are you saying your teacher told you that A and C cannot be solved? That's true, strictly speaking, but in the absence of further detail I would have assumed the acceleration during that 7.5 seconds was constant, and solved accordingly.