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Finding final velocity.

  • Thread starter BuhRock
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  • #1
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1. Determine the acceleration of an object whose velocity is initially 24 cm/s and which accelerates uniformly through a distance of 66 cm in 3.8 seconds.




2. s = (vf + v0) / 2 * t,



3. I tried rearranging that formula but I got vf= 477.6. This just doesn't make any sense
 

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  • #2
1. Determine the acceleration of an object whose velocity is initially 24 cm/s and which accelerates uniformly through a distance of 66 cm in 3.8 seconds.




2. s = (vf + v0) / 2 * t,



3. I tried rearranging that formula but I got vf= 477.6. This just doesn't make any sense
Didnt you just find the final velocity? they asked for acceleration, so you should be solving for that since you have the time. you can find out the acceleration
 
  • #3
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I was saying that the vf being 477.6 doesn't make sense. Also, how can I find a with just t.
 
  • #4
I was saying that the vf being 477.6 doesn't make sense. Also, how can I find a with just t.
Determine the kinematic equation that you would have to use.....

Vf = Vi + at
Delta x = .5(vf+vi)t
Delta x = Vi(t)+.5a(t^2)
Vf^2 = Vi^2 + 2a(delta x)

Choose which one you would use, and solve for Vf.
 
  • #5
SammyS
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2. s = (vf + v0) / 2 * t,



3. I tried rearranging that formula but I got vf= 477.6. This just doesn't make any sense
You apparently interpreted the equation as being s = (vf + v0) / (2 * t)

However the equation is equivalent to s = ((vf + v0) / 2) * t
 
  • #6
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With uniform acceleration, can you say that average velocity * 2 = vf?

Determine the kinematic equation that you would have to use.....

Vf = Vi + at
Delta x = .5(vf+vi)t
Delta x = Vi(t)+.5a(t^2)
Vf^2 = Vi^2 + 2a(delta x)

Choose which one you would use, and solve for Vf.
Well I don't have acceleration. I was thinking I would use the second one, but I don't have vf. What is delta x?
 
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  • #7
SammyS
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You can find average velocity. From that and the initial velocity you can find final velocity. Then acceleration.
 
  • #8
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I tried taking the equation s = .5(vo+vf)t and rearranging it to get vf, which got me 10.7 which can't be right. What is the delta x in those equations?

I have initial velocity, which is 24 m/s. I have average velocity which is 17.36(Displacement / time). So, from here. What do I use?
 
  • #9
SammyS
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vf = 10.737 m/s is about right.

The initial velocity is greater than the average velocity, so the object is slowing down.

Now find the acceleration.
 

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