Answers

1. Answer:

   Explanation:

   In order to measure the coefficient of friction , we apply external force to move the body . When external force comes in motion , we adjust the external force so that it moves with zero acceleration or uniform velocity . In this case external force becomes equal to kinetic frictional force and then net force becomes zero because

   net force = mass x acceleration = m x 0 = 0

   Now frictional force = μ mg where μ is coefficient of kinetic friction

   so F = μ mg where F is external force applied

   μ = F / mg

   Hence , to make external force equal to frictional force , it is necessary to make acceleration of body zero .

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