anonymous
  • anonymous
Suppose that you toss a rock upward so that it rises and then falls back to the earth. If the acceleration due to gravity is 9.8 m/sec2, what is the rock’s acceleration at the instant that it reaches the top of its trajectory (where its velocity is momentarily zero)? Assume that air resistance is negligible.
Physics
  • Stacey Warren - Expert brainly.com
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SOLVED
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katieb
  • katieb
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anonymous
  • anonymous
- The acceleration of the rock is zero. - The rock has an upward acceleration of 19.6 m/s2. -The rock has a downward acceleration of 19.6 m/s2. -The rock has a downward acceleration of 9.8 m/s2. -The rock has an upward acceleration of 9.8 m/s2.
theEric
  • theEric
What is your initial thought, @pretty27 ?
anonymous
  • anonymous
downward acceleration of 9.8 m/s2

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More answers

anonymous
  • anonymous
It will be constant during the path even if it stops for a second. But If we consider the air effect during the falling, then it CAN be zero in this case. thus it will depend on the problem you are given.
anonymous
  • anonymous
its mult choice and those are the choices given.. but i dont know.. I am second guessing this question
theEric
  • theEric
I think you are right, @pretty27 !
theEric
  • theEric
That acceleration is constant, neglecting air friction, changing gravity, and other negligible forces.
theEric
  • theEric
In your course, you ignore those, and acceleration is only that which is due to gravity!
anonymous
  • anonymous
ohh its downward of 9.8 m/s2 ..people is class are telling me all different answers but thanks for clearing it out1
anonymous
  • anonymous
out! *
theEric
  • theEric
And I mean, due to gravitational force on the mass due at around Earth's surface.
Shane_B
  • Shane_B
So now that this question has been answered 3 times in 24 hours, has the answer changed? :)
theEric
  • theEric
Haha, if you post their arguments, we can refute them if it will help you!
anonymous
  • anonymous
If the positive direction of y-axis is chosen to be upwards, then, for the time it is to fall, we have a downwards acceleration -9.8 m/s^2.
anonymous
  • anonymous
nope thanks Shane_B , theEric & Saeeddiscover for your help! just wanted to clear this out
anonymous
  • anonymous
I have one last question if you guys can help me out .. please
theEric
  • theEric
@Saeeddiscover , In that "up is positive" and "down is negative" system, we have downward acceleration that is \(-9.8\ [m/s^2]\). But we have a downwards acceleration with a magnitude of \(9.8\ [m/s^2]\). The choices could be more clear, but there is that one acceptable answer :)
theEric
  • theEric
So like you said, acceleration is \(-9.8\ [m/s^2]\) with up being positive.
theEric
  • theEric
:)
anonymous
  • anonymous
so - is downward and + is upward right?
theEric
  • theEric
The positive and negative directions can be defined however you want! But, most often, everybody says what you just said, that positive is up and negative is down.
theEric
  • theEric
:)
theEric
  • theEric
Also, feel free to post your last question when you are ready!
anonymous
  • anonymous
oki thank you
anonymous
  • anonymous
I have only 15 minutes to stay. But others are still on the opensstudy.
theEric
  • theEric
Yep, that is the benefit of a large community!
anonymous
  • anonymous
When an object is thrown upward, it will keep going until comes a stop. during the time fly the speed is slowing down and it would make a negative acceleration -9.8 if one of coordinates x, y, or z is directed upward. And a positive one when falling downward....
theEric
  • theEric
The object will slow down, yes. Now, let's suppose one axis is directed upward. Then the upward direction is positive. The change in velocity, then, would be from upwards (positive) to \(0\). The change in velocity was a negative change, and so acceleration would be negative. As the object comes down, its velocity changes from \(0\) to downward (negative). This change is also a negative change. So acceleration is still negative.
anonymous
  • anonymous
Yes it is a correct context. I think it will stay negative for both directions. Can you see a symmetric in direction?
theEric
  • theEric
A symmetry in direction?
anonymous
  • anonymous
The acceleration is negative for both directions whereas the velocity vector changes two times during the flying. it is a dramatic motion!
theEric
  • theEric
Ah, I was wondering if that was what you meant! Yes, the change in position is first positive and then negative! All while position is positive and acceleration is negative! It's fun to think about!

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