Q4. A cylindrical body, 90 mm in dimeter and 500 mm long and of weight 15 N. slides vertically down a 92 mm cylindrical sleeve due to its own weight. The space between the body and the sleeve is filled with oil. Determine the dynamic viscosity of the oil needed to restrict the velocity of fall of the cylindrical body to 5 cm/s. (Assume linear variation of velocity across the gap).