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    • Thread Starter

    The question is a s follows:
    In loading a delivery van, the driver pushed 15kg crate for 5 metres up a ramp. She had to push with a force of 132N and the vertical height was 1.3 m. What was the efficiency of pushing this crate up the ramp onto the back of the van?
    The answer is 20%, however I cant comprehend how this answer was obtained.

    What is the useful energy in this case? would it be considered the vertical or horizontal one?
    My answer is 82% since I took the useful energy to be the horizontal and for the total energy I used horizontal+vertical.
    Please help.

    I assume you've worked out that the total energy is about 854J and the energy required to move alone the horizontal is about 682J. So the wasted energy is about 172J (854-682). Put 172/854 and times by 100 that will give you about 20%.
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