Christos
  • Christos
physics, can someone help me solve part b of this problem https://www.dropbox.com/s/8uwrpl0h3fcm1r8/Screenshot%202015-12-13%2018.58.35.png?dl=0
Mathematics
  • Stacey Warren - Expert brainly.com
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SOLVED
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chestercat
  • chestercat
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phi
  • phi
what did you get for part A?
phi
  • phi
using v= a*t and d= 0.5 a * t^2 then d/v = 0.5t and t= 2d/v where d is distance traveled and v is the final velocity
phi
  • phi
after distance d, there is 100-d still to go, at velocity 11 thus the total time to run the race is 2d/v + (100-d)/v = 10 seconds here v is 11 and we want to solve for d

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Christos
  • Christos
@phi for a i got 13
Christos
  • Christos
13,04 seconds
phi
  • phi
How?
Christos
  • Christos
i used kinematic equations
phi
  • phi
can you post them? I get a different result for A
Christos
  • Christos
sec
Christos
  • Christos
https://www.dropbox.com/s/wy2orousogw0od7/Screenshot%202015-12-14%2014.48.58.png?dl=0
phi
  • phi
that all looks ok, except I don't see how you get 13 seconds isn't it 24/11 seconds to accelerate to 11 m/s^2 and 8 seconds to complete the race? that adds up to 10 2/11
phi
  • phi
you must have added the acceleration (5.04) to 8 seconds to get 13.04 you want to use the time V= a * t 11 = 121/24 * t t= 24*11/121 = 24/11 = 2 and 2/11
Christos
  • Christos
10,18 seconds ?
phi
  • phi
We know the initial velocity and distance are zero, so the equations simplify to just \[ v_f = a t \\ x= \frac{1}{2} a t^2 \] or \[ 2x= a t^2\\ v_f= a t\] if we divide the equations (i.e. divide the left sides and right sides) we get \[ \frac{2x}{v_f}= t \] we are told x is 12 m and v_final = 11 m/s^2 so we find \[ \frac{2\cdot 12}{11}= t \\ t= \frac{24}{11} = 2.1818...\] and total time is 8 + 2.1818= 10.1818...
phi
  • phi
For part B, we can use that same equation for the time to accelerate to v_final \[ t_1= \frac{2x}{11} \] and the time to complete the race is \[ t_2= \frac{100-x}{11} \] and the total time is \[ t_1+t_2= 10 \]
Christos
  • Christos
i see
phi
  • phi
You can finish the problem?
Christos
  • Christos
I think I can yes
Christos
  • Christos
(x1 - 0 + x2 - x1) / 11
phi
  • phi
what is x2?
phi
  • phi
to find the distance x in Part B , the equation is \[ \frac{2x}{11}+ \frac{100-x}{11} = 10 \\ 2x + 100 -x = 110 \\ x+100 = 110\\ x= 10\]

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