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8th Class Science Friction Question Bank Friction IIT JEE Objective Problems

  • question_answer
    A car designer designed four cars labelled as I, II, III, and IV. The shapes of the cars are shown in given figure. On a test drive, these cars are moving with the same speed on a highway. The tank of each car is filled with the same quantity of fuel.
    In covering equal distances, least fuel is consumed by car

    A)  I                                             

    B)  II                 

    C)  III                                          

    D)  IV

    Correct Answer: C

    Solution :

      A force of friction arises when two objects move in contact with each other. The opposing force that acts on an object that is moving in a fluid (air) is called drag. An object that is moving in air must overcome this opposing drag. The presence of drag reduces the speed. The magnitude of drag depends on the shape of the object. Drag is the minimum when the moving object is of streamline shape. In the given situation, the shapes of all four cars are different. Therefore, the fuel consumption in each will be different because each will be opposed by different drags. Greater the drag, more is the fuel required to move the car a certain distance and vice-versa. Here, only car III is streamline in shape. Therefore, it will experience least amount of drag against its motion. As a result, it will consume less fuel as compared to the other cars in covering the same distance. The correct answer is C.


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