Force and Acceleration 3


M (kg)
1  3 5






A grey mass m=1kg is via a massless string attached to a red mass M. The string can move freely over a massless pulley. At t=0 the mass m is released, while the string is stretched to its full length.
The sliding mass M feels a frictional force with the table. It can be expressed as μFN with FN the normal force of the mass M on the table. μ has a value of 0.3. The graph on the right side of the screen shows the velocity of m as a function of time.

  • Describe the motion of m and M.
  • Write down Newton's equation of motion for m and for M.
  • Solve these equations and find the critical value of μ for which the masses just move.
  • Is this value in agreement with the physlet?
  • Is the acceleration of m constant? Why (not)?

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