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    Ok, I've learned the formula for Impulse to be Impulse = M(V-U), but then there's also a bit = FT and I know that it stands for Force x Time. However, I'm a bit unsure of when to use it. Sometimes I think there have been questions where I just use the M(V-U) bit and now I'm looking at the mark scheme for a question where they have used the FT bit as well. So how do you know when to use it? Is it *always* used or just in some instances?
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    (Original post by SMC879)
    Ok, I've learned the formula for Impulse to be Impulse = M(V-U), but then there's also a bit = FT and I know that it stands for Force x Time. However, I'm a bit unsure of when to use it. Sometimes I think there have been questions where I just use the M(V-U) bit and now I'm looking at the mark scheme for a question where they have used the FT bit as well. So how do you know when to use it? Is it *always* used or just in some instances?
    Depends on the info you're given - often you know what the change in momentum of a particle or object is, but you don't know the time interval over which a force acts; or it may be an instantaneous change in momentum in which case you need the mv-mu version.
 
 
 
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