Vectors: Average Velocity, Acceleration, Speed

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Homework Help Overview

The discussion revolves around a physics problem involving a car's motion, specifically focusing on average velocity, average acceleration, and average speed over a specified time interval. The subject area includes kinematics and vector analysis.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants explore the implications of the given velocities and the time interval, questioning whether the car's speed changed gradually or abruptly. There is a focus on the need to determine the components of velocity and how time factors into the calculations.

Discussion Status

Some participants have expressed uncertainty about the ability to solve parts A and C of the problem, while others have suggested that assuming constant acceleration might allow for progress in calculating average acceleration. The discussion indicates a mix of interpretations regarding the problem setup.

Contextual Notes

There is a noted ambiguity in the problem regarding the nature of the car's velocity change and the assumptions that can be made about the motion during the time interval. Participants are also considering the definitions of average velocity and speed in their analysis.

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Homework Statement



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,
 
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END said:

Homework Statement



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 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.

END said:
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,

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
 
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.
 
END said:
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.

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.
 

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