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    A crane is lifting a car of load 850 kg. It lifts the car 12m in 40s. The crane has 60% efficiency. Find the input power of the crane. I had this question for my mock. I used P=F/v but unsure. The first part of this question was to find T. Please help thanks.
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    Refer to post below.
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    There is another formula for power, which is power = work done/time taken

    First work out the amount of gravitational potential energy car will have when fully lifted, which is worked out by: G.P.E (gravitational potential energy)= mass * gravitational field strength * height
    so...G.P.E = 850 * 9.81 * 12 = 100062 Joules

    Then it says crane has 60% efficiency, so the G.P.E equivalent is the 60% of total energy inputted, so you work out what 100% is, which is done by:
    (work out 40%)..(100062/3)*2=66708
    When you add 40% to 60%, you get 100%, so 100062 + 66708 = 166770 Joules

    Then use the power equation
    Power = 166770/12 = 4169.25 W required as input

    Can you clarify what T is? Is it tension?
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    (Original post by Outofthisworld)
    A crane is lifting a car of load 850 kg. It lifts the car 12m in 40s. The crane has 60% efficiency. Find the input power of the crane. I had this question for my mock. I used P=F/v but unsure. The first part of this question was to find T. Please help thanks.
    Just out of curiosity, is this for mechanics maths or physics?
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    (Original post by G.Y)
    Just out of curiosity, is this for mechanics maths or physics?
    Physics since you had to use power formula and the thread title also says physics
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    Yes T was tension, I got the same answer as you but I did P=Fv or work done/time then divide by 0.6. But I like your explanation of using G.P.E, it's makes more sense cause we know that the crane did work against gravity to bring the car to 12m.
    Thanks!
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    Yes, I think I got the answer. It was 4 mark so I was thinking it's too simple and so many marks just for this question. But I got this .
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    (Original post by neluxsan)
    Physics since you had to use power formula and the thread title also says physics
    Lol whoops
 
 
 
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