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    a car of mass 1000kg is towing a trailer of mass 1500kg along a straight horz road. The tow bar joining the car to the trailer is modelled as a light rod parallel to the road. The totl resistance to motion of the car is modelled as having magnitude 750 N and is constant. The total resistance to motion of the trailer is modelled as having magnitude R where R is a constant. When the engine of the car is working at a rate of 50kw the car and the trailer travel at a constant speed of 25m/s.

    a) show that R=1250 I could do tis bit but....

    When travelling at 25m/s the driver disengages the engine and applies the brakes. The brakes provide a constant braking force of magnitude 1500N to the car. The resisting forces of magnitude 750N and 1250 N are assumed to remain unchanged.

    b) calculate the deceleration of the car while braking
    this is where i got stuck the answer is 1.4

    please help me!!!
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    force from engine = 0N
    F=ma
    0 - 1500 - 750 - 1250 = 2500a
    -3500 = 2500a
    -3500/2500 = a = -1.4ms-2
    = 1.4ms-2 deceleration
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    duhhh!!! i thought there was still a force from the engine. there really is no hope for me lol :rolleyes: cheers xxx
 
 
 
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Updated: June 21, 2005
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