JEE Main & Advanced Physics NLM, Friction, Circular Motion JEE PYQ - NLM Friction Circular Motion

  • question_answer
    A car of mass 1000 kg is moving at a speed of 30 m/s. Brakes are applied to bring the car to rest. If the net retarding force is 5000 N, the car comes to stop after travelling dm in t s. Then [JEE ONLINE 07-05-2012]

    A) \[d=150,t=5\]

    B) \[d=120,t=8\]

    C) \[d=180,t=6\]

    D) \[d=90,t=6\]

    Correct Answer: D

    Solution :

    [d] Given: mass of car m = 1000 kg u = 30m/s
    v = 0 m/s retarding force f = 5000 N
    \[\therefore \]retardation, \[-a=\frac{5000}{1000}=5\,m/{{s}^{2}}\]
    By equation, \[{{v}^{2}}-{{u}^{2}}=2as\]
    \[0-{{(30)}^{2}}=-2\times 5\times d\]
    \[\therefore \]\[d-\frac{900}{10}=90m\]
    and\[a=\frac{v-u}{t}\therefore t=\frac{v-u}{a}=\frac{0-30}{-5}=6s\]


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