Why is it more difficult to walk on smooth ice than on a rough concrete road?

Introduction / Context:
This question examines your understanding of friction and its role in walking. In everyday life, we know that walking on a smooth icy surface is slippery and difficult, whereas walking on a rough concrete road feels safer. The underlying reason is related to the amount of friction between your feet (or shoes) and the surface. This concept is fundamental in mechanics and is frequently tested in general physics and aptitude exams.

Given Data / Assumptions:

• The surfaces being compared are ice and rough concrete.
• A person is attempting to walk normally on both surfaces.
• No special footwear with spikes or grips is being used.
• We assume that the main forces at play are normal reaction and friction between foot and ground.

Concept / Approach:
Friction is the resistive force that opposes relative motion between two surfaces in contact. Static friction is necessary for walking, because when you push backward on the ground with your foot, friction pushes you forward. If friction is too small, the foot slips instead of gripping the surface, and you cannot walk effectively. Ice is smooth and often has a thin layer of water on top, making the coefficient of friction between shoe and ice very small. Concrete, being rough and dry, offers a much higher friction. Therefore, low friction on ice is what makes walking difficult, not higher friction or softness of the material.

Step-by-Step Solution:
Step 1: Recall that to walk, your foot must push backward on the ground so that friction can push you forward. Step 2: Understand that sufficient static friction is needed to prevent your foot from slipping when you push. Step 3: On a rough concrete road, the coefficient of friction between shoe and ground is relatively high, providing good grip. Step 4: On ice, the surface is smooth and often partially melted, resulting in a very low coefficient of friction. Step 5: Low friction on ice means that when you push backward, your foot tends to slip instead of gripping, making walking difficult. Step 6: Therefore, the difficulty arises because there is very little friction between the ice and the feet pressing it.

Verification / Alternative check:
You can verify this by observing people slipping more easily on icy pavements than on dry ground. Special shoes with spikes or shoes for ice skating increase friction or use controlled sliding to manage motion on ice. In contrast, rubber soles on concrete generally provide good traction. Textbook examples and experiments, such as sliding blocks on different surfaces, also show that smoother surfaces like ice reduce friction, while rough surfaces like concrete increase it. All these observations support the conclusion that low friction is the main cause of difficulty when walking on ice.

Why Other Options Are Wrong:
Ice is soft compared to concrete: Softness is not the primary factor here; even if a material is soft, what matters is the frictional force available for walking.
There is more friction between the ice and the feet: This is the opposite of the true situation. More friction would actually make walking easier, not harder.
None of these: Since one option clearly matches the correct explanation, this catch-all option is incorrect.

Common Pitfalls:
A common misunderstanding is to think that less friction is always better because it allows smoother motion. However, for walking, turning, and stopping safely, a certain minimum friction is essential. Another pitfall is confusing hardness or softness with friction; they are not the same property. When solving such questions, always focus on how friction helps or hinders the motion being described.

Final Answer:
It is more difficult to walk on ice because there is very little friction between the ice and the feet pressing it.