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    energy.docx

    There's the question and mark scheme on the attachment. I'm stuck on part c, the final part.

    Power=work done/time

    Energy=work done

    So energy/power=time. I understand how they got this. But I can't understand how they worked out power as power=force X velocity. They divided the velocity of 1.33 by 2, but why?

    Thank you so much
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    (Original post by krisshP)
    energy.docx

    There's the question and mark scheme on the attachment. I'm stuck on part c, the final part.

    Power=work done/time

    Energy=work done

    So energy/power=time. I understand how they got this. But I can't understand how they worked out power as power=force X velocity. They divided the velocity of 1.33 by 2, but why?

    Thank you so much
    velocity=distance/time
    work done=force(component in direction of motion) x distance

    so force=work done/distance

    so force x velocity=(work done x distance)/(time x distance)=Power

    Without really looking at it I'd say that the division by two would be a result from energy lost in the collision as it is inelastic. You could work this out from conservation of momentum.
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    (Original post by krisshP)
    energy.docx

    There's the question and mark scheme on the attachment. I'm stuck on part c, the final part.

    Power=work done/time

    Energy=work done

    So energy/power=time. I understand how they got this. But I can't understand how they worked out power as power=force X velocity. They divided the velocity of 1.33 by 2, but why?

    Thank you so much
    Because the velocity is not constant. The trucks slow down from 1.33m/s to zero and 1.33/2 is the average velocity. You need force x average velocity to calculate the (average) power over that time interval.
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    (Original post by Stonebridge)
    Because the velocity is not constant. The trucks slow down from 1.33m/s to zero and 1.33/2 is the average velocity. You need force x average velocity to calculate the (average) power over that time interval.
    Oh yeah, that does make sense now

    Thanks for the help
 
 
 

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