Why is skating on ice possible even though the blades of the skates are narrow and the contact area is small?

Introduction / Context:
Ice skating is a common example used in physics to illustrate the effect of pressure on the melting point of ice and the role of a thin water layer in reducing friction. Even though the blades of skates are very narrow and exert large pressure on the ice, skaters can glide smoothly over the surface. This question tests whether you understand the physical explanation behind this phenomenon, which combines ideas from thermodynamics and friction.

Given Data / Assumptions:

• Skate blades have a small area of contact with the ice surface.
• The skater's weight acts through the blades on the ice, creating high pressure.
• The environment is at or near the freezing point of water.
• The question asks how this situation makes skating possible and smooth.

Concept / Approach:
According to the pressure melting concept, when pressure on ice increases, its melting point decreases slightly. Under the high pressure from the sharp skate blades, the ice at the contact region can melt even if the ambient temperature is slightly below 0°C. This forms a very thin film of water between the blade and the underlying ice. Water has a much smaller coefficient of friction than solid-to-solid contact, so this lubricating layer allows the skate to glide smoothly. As pressure is removed, the water refreezes, and the process repeats continuously as the skater moves.

Step-by-Step Solution:
Step 1: Recognise that the skater's weight concentrated on thin blades creates very high pressure on the ice.Step 2: Understand that increased pressure slightly lowers the melting point of ice beneath the blades.Step 3: The ice under the blades can partially melt, forming a thin film of water.Step 4: This thin water film acts as a lubricant between the blade and the ice surface.Step 5: The lubricating film significantly reduces friction and allows smooth gliding.Step 6: After the blade passes, pressure decreases and the thin water film refreezes.

Verification / Alternative check:
If skating were only due to a smooth solid surface, people would be able to glide equally well on smooth concrete with metal blades, which is not the case. The uniquely low friction of ice near its melting point and the behaviour of thin water films are key. Also, frictional heating contributes to maintaining the water layer as the skate moves, which supports the idea that a thin film of water is present and responsible for easy sliding.

Why Other Options Are Wrong:
The statement that the surface of ice is smooth is partly true, but smoothness alone does not explain the extremely low friction observed in skating. Saying that ice is cold is trivial and does not clarify why sliding is easy. The option claiming that pressure raises the melting point is physically incorrect; for ice, increased pressure lowers the melting point. Therefore, these options fail to capture the correct underlying mechanism.

Common Pitfalls:
A common misconception is to think purely in terms of smoothness, ignoring the role of phase change and the water layer. Another mistake is not knowing that the melting point of ice decreases with increasing pressure, which is opposite to what some students guess intuitively. To handle such questions, remember that pressure melting plus a lubricating water film together explain why skating is easy on ice but not on most other smooth surfaces.

Final Answer:
Skating on ice is possible mainly because the high pressure of the skate blade lowers the melting point of ice, forming a thin film of water that allows smooth sliding.