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    Hey, I have got an answer to this question very close to the one in the answers- I get 25410 and they get 25400, so they may be giving it to 3SF, but would just like someone to check my working...

    A lorry of mass 15000kg is moving up a straight road inclined at an angle x to the horizontal where sinx=0.25.
    The lorry is travelling at aconstant speed of 12m/s and the constant resistance to its motion has mag 175kN.
    Find the work done in 10s by the engine of the lorry.

    My working:
    (F is driving force up slope)

    resolve parallel to slope:
    F-175000- 0.25x15000g = 15000 x 0
    F = 211750

    Power = Fv
    = 211750 x 12
    = 2541000

    Since power is work done per s, work done in 10s = power x 10,
    = 25410000 W
    = 25410 kW

    thank you!!!
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    Looks good to me.
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    Probably just a printing error - there's LOADS in my GCSE textbook. I suspect that they put in the odd false answer to try and catch cheaters out (answers are at the back of the book) :rolleyes:
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    (Original post by franks)
    Hey, I have got an answer to this question very close to the one in the answers- I get 25410 and they get 25400, so they may be giving it to 3SF, but would just like someone to check my working...

    A lorry of mass 15000kg is moving up a straight road inclined at an angle x to the horizontal where sinx=0.25.
    The lorry is travelling at aconstant speed of 12m/s and the constant resistance to its motion has mag 175kN.
    Find the work done in 10s by the engine of the lorry.

    My working:
    (F is driving force up slope)

    resolve parallel to slope:
    F-175000- 0.25x15000g = 15000 x 0
    F = 211750

    Power = Fv
    = 211750 x 12
    = 2541000

    Since power is work done per s, work done in 10s = power x 10,
    = 25410000 W
    = 25410 kW

    thank you!!!
    actually, all the answers at the back are given to 3 sig figures
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    actually, all the answers at the back are given to 3 sig figures
    really?! lol, shows how much attention I pay !!! :rolleyes:
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    Why is Work done given in Watts, rather than in Joules?
 
 
 
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