A driver notices that her 1280 kg car slows down from 92 km/h to 68 km/h in about 7.5 s on the level when it is in neutral. Approximately wh

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A driver notices that her 1280 kg car slows down from 92 km/h to 68 km/h in about 7.5 s on the level when it is in neutral. Approximately what power (in watts) is needed to keep the car traveling at a constant 80 km/h

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Diễm Kiều 4 years 2021-07-31T22:00:52+00:00 1 Answers 13 views 0

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    2021-07-31T22:02:38+00:00

    Answer:

    P = 25299.75 watts

    Since 80km/h is the average speed of 92km/h and 68km/h, the power (in watts) is needed to keep the car traveling at a constant 80 km/h is P = 25299.75 watts

    Explanation:

    Given;

    Mass of car m = 1280kg

    initial speed v1 = 92km/h = 92×1000/3600 m/s= 25.56m/s

    Final speed v2 = 68km/h = 68×1000/3600 m/s= 18.89m/s

    time taken t = 7.5s

    Change in the kinetic energy of the car within that period;

    ∆K.E = 1/2 ×mv1^2 – 1/2 × mv2^2

    ∆K.E = 0.5m(v1^2 -v2^2)

    Substituting the values, we have;

    ∆K.E = 0.5×1280(25.56^2 – 18.89^2)

    ∆K.E = 189748.16J

    Power used during this Change;

    Power P = ∆K.E/t

    Substituting the values;

    P = 189748.16/7.5

    P = 25299.75 watts

    Since 80km/h is the average speed of 92km/h and 68km/h, the power (in watts) is needed to keep the car traveling at a constant 80 km/h is P = 25299.75 watts

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