Скачать или смотреть PHYSICS MADE EASY - Why we need Friction for Walking

Hi, this video explains why we are able to walk, how we tend to slip. Walking is made possible by static friction existing between the bottom surface of our feet or shoe soles and the surface of the Road , or floor in our homes. The force of friction is then same , F = (mu)N where N is the Normal Force exterted on the ground by our weight.
If this static friction force was totally absent, i.e. F=0, we may see total slip and remain where we are standing. This can happen on an icy surface when ice has melted on the top contact surface.
The static friction co-efficient applies here.

During RUNNING, you may see that shoes are having a slight slip with respect to the ground, as shown in the animation, and in this case, Dynamic Friction is applicable instead of Static friction.

The Normal Force 'N' applied may be greater during running or jogging as the human body falls from a small height on to the ground and F=ma . Then, Friction Force 'F' is also greater because F is proportional to the Normal Force 'N'.

Animals with 4 legs would distribute their Normal Force 'N' at the contact points of their 4 legs, the mass of animal gets distributed as N/4. Then at each point, Static F=(mu)(N/4) .

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