Vectors: Average Velocity, Acceleration, Speed

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The discussion revolves around a physics homework problem involving a car's velocity and acceleration over a time interval. Participants express uncertainty about whether the car's speed changed gradually or instantaneously, impacting the calculations for average velocity and speed. It is concluded that the average velocity and speed cannot be determined without additional information about the car's motion during the 7.5 seconds. However, average acceleration can be calculated by breaking down the velocity vectors into their components. The conversation emphasizes the importance of understanding vector components and the definitions of average velocity and acceleration in solving the problem.
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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.
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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