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JAMB Physics 1986 Question 11

Question 11

Friction

When a box of mass 45 kg is given an initial speed of 5 m s−1, it slides along a horizontal floor a distance of 3 m before coming to rest. What is the coefficient of the kinetic friction between the box and the floor? (g = 10 m s−2)

  1. A.5/6
  2. B.5/12
  3. C.1/3
  4. D.2/3.
Show the answer and explanation

Answer: B (5/12)

Explanation

Deceleration a = u²/2s = 25/6 m s−2. Friction μmg = ma, so μ = a/g = (25/6)/10 = 5/12.