Calculating Average Drag Through Plasticene

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Average drag refers to the retarding force experienced by an object, such as a bullet, as it moves through a medium like plasticine. In this case, a bullet weighing 200g traveling at 100m/s encounters an average drag of 5000 N while passing through three pieces of plasticine. The work done by this drag force results in a reduction of the bullet's kinetic energy, which can be calculated using the work-kinetic energy theorem. The relevant formula is EK_final - EK_initial = W_drag, indicating that the drag force does negative work on the bullet, ultimately bringing it to a stop. Understanding these principles allows for the calculation of how far the bullet will penetrate the plasticine.
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Average drag??

Hi' this is my first post here:rolleyes: , What is average drag:confused: :rolleyes: (underlined bit) eg,
I shot a bullet thru three pieces of plasticene(15cm thickness each) each placed 5 cm apart and the average drag of the plasticene is 5000 N the bullet has a mass of 200g was traveling at 100m/s how far will the bullet go through the plasticane ?? :shy: I'd like to know how to work that out as well :wink: :cool:
thanks a lot guys:wink::cool:
 
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Drag is the average retarding force that an object (in this case the bullet) experiences as it moves through the medium (plasticine). The plasticine therefore generates friction that slows the bullet down as it moves through it. The drag force will do work on the bullet causing a reduction of its kinetic energy. If we ignore other forces acting on the bullet we can say that:
the work done on the bullet by the drag force acting on it = the change in the kinetic energy of the bullet
using the work-kinetic energy theorem.
 
Oh:bugeye: , I see now, thanks alot, can I use this formula to solve this problem??
E2 = E1 + W21 ??
0 = 1/2 MV2 + f.S ??

I don't know whether its a right formula or not please correct if I'm wrong:redface: :frown:
thanks again!:cool:
 
Yes, your formula can be rewritten as
EK_{final}-EK_{initial}=W_{drag}
where EK is the kinetic energy of the bullet and W_{drag} is the work done by the drag force on the bullet. That is the friction on the bullet is removing kinetic energy from the bullet as it moves throught the plasticene. The above equation reduces to
-EK_{initial}=W_{drag}
since the final kinetic energy of the bullet is zero - it came to a stop - as you showed in your equation above. What to do about the negative sign??!

Well, the work done by the drag on the bullet is negative!
 
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