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9th Class Science Force and laws of motion Question Bank Force and Laws of Motion

  • question_answer
    A particle of mass 100 g is suspended from a light string. The string is moved [a] Upwards, and [b] Downwards with an acceleration of\[\text{5 m}/{{\text{s}}^{\text{2}}}\]. If \[{{T}_{u}}\] and \[{{T}_{d}}\] are the tension in the string during upward and downward motion respectively, then \[{{T}_{u}}-{{T}_{d}}\] is equal to

    A)  1N                          

    B)         0.5 N

    C)  0.98 N             

    D)         1.96 N

    Correct Answer: A

    Solution :

     During the upward motion                 \[{{T}_{u}}-mg=ma\]                                      ? (i) During the downward motion             \[mg-{{T}_{d}}=ma\]                            ... (ii) Adding equations, (i) and (ii) we get             \[{{T}_{u}}-{{T}_{d}}=2ma=1\,\,N\]


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