Question

An ice skater glides on one skate, across a thin film of water that forms on the ice surface due to the pressure exerted by the skater. However, the water lm that supports the skate also causes deceleration (so does drag on the body of the skater with the air, but consider only the skate and water film here).

The skater has a mass of 55 kg. The skate contact surface is 29 cm long and 3 mm wide. The water film formed is just 1.5×10–6 m thick, and the ice-water in the film has a viscosity of 1.897 mPa*s. The skater is initially gliding along at 5.4 m/s.

(a) Determine the pressure exerted on the ice surface, as a gauge pressure (you may safely ignore am- bient pressure here).

(b) Determine the shear stress exerted on the ice surface, assuming that the velocity (U) across the water lm (thickness h) varies linearly, so that

dU/dz ≈ U/h

(c) Determine the deceleration of the skater, at a velocity of 5.4 m/s.

(d) The skater continues to glide forward. Determine the time required for their velocity to decrease to 4 m/s. Note that the deceleration is not constant.

Answer 1