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    A particle is moving along the x-axis with constant deceleration 5ms-2. At time=0, the particle passes through the origin o with velocity 12ms-1 in the positive direction. At time t secounds the particle passes through the point A with x-coordinates 8. Find the values of t.

    Any help?

    I know the formula that is used is s=ut+1/2at^2 but I keep getting the wrong answer.
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    (Original post by Mist786)
    A particle is moving along the x-axis with constant deceleration 5ms-2. At time=0, the particle passes through the origin o with velocity 12ms-1 in the positive direction. At time t secounds the particle passes through the point A with x-coordinates 8. Find the values of t.

    Any help?

    I know the formula that is used is s=ut+1/2at^2 but I keep getting the wrong answer.
    a=-5
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    (Original post by rbnphlp)
    a=-5
    I still get the wrong answer.I sustituted the values
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    u=12
    a= -5
    s=8
    t= ?
    s= ut + 1/2 at^2
    8= 12t -2.5t^2
    5t^2-24t+16=0
    (5t-4)(t-4)=0
    t=4, t=0.8
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    (Original post by Revolution is my Name)
    u=12
    a= -5
    s=8
    t= ?
    s= ut + 1/2 at^2
    8= 12t -2.5t^2
    5t^2-24t+16=0
    (5t-4)(t-4)=0
    t=4, t=0.8
    Thanks
    btw, cool profile
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    (Original post by Mist786)
    A particle is moving along the x-axis with constant deceleration 5ms-2. At time=0, the particle passes through the origin o with velocity 12ms-1 in the positive direction. At time t secounds the particle passes through the point A with x-coordinates 8. Find the values of t.

    Any help?

    I know the formula that is used is s=ut+1/2at^2 but I keep getting the wrong answer.
    a= -5ms-2
    u = 12ms-1
    s = 8

    Sub in the values and rearrange into a quadratic and solve
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    How'd you solve it if the next question was: Find the velocity of the particle as it passes through the point with x-coordinate -8
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    (Original post by Mist786)
    How'd you solve it if the next question was: Find the velocity of the particle as it passes through the point with x-coordinate -8
    Sub in s=-8 instead and see what happens?
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    (Original post by Revolution is my Name)
    Sub in s=-8 instead and see what happens?
    I get the wrong answer because the question asks what is the velocity not time
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    (Original post by Mist786)
    I get the wrong answer because the question asks what is the velocity not time
    Well, you've got u=0, s=-8, a=-5, and are trying to find v; do you know an equation of motion linking those four?
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    You may be expected to use more than one SUVAT equation in one question if it's long, so don't confine yourself to just the s=ut+1/2at^2.
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    (Original post by Revolution is my Name)
    Well, you've got u=0, s=-8, a=-5, and are trying to find v; do you know an equation of motion linking those four?
    If I use the formula v^2=2as-u^2, I stll get the wrong answer when I substitute usa in the formula. How is u=0?
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    (Original post by Mist786)
    If I use the formula v^2=2as-u^2, I stll get the wrong answer when I substitute usa in the formula. How is u=0?
    Ah sorry, u=12; I'm a bit too used to doing these starting from rest.
    I'm pretty sure the equation is actually v^2=u^2+2as; try it with that and see if that gives you the right answer.
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    (Original post by Revolution is my Name)
    Ah sorry, u=12; I'm a bit too used to doing these starting from rest.
    I'm pretty sure the equation is actually v^2=u^2+2as; try it with that and see if that gives you the right answer.
    Okay, cool

    Thanks
 
 
 
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