You would start sliding forever or trip in an instant and would not be able to stand up and walk properly without holding onto an object. Because friction is what keeps your feet remain still on the ground.
If there was no friction between the soles of your shoes and the sidewalk, you would be endlessly sliding down it until your momentum stopped you or you ran out of force.
You would increase friction so that you wouldn't slip, by using the brakes on your car of bike you increase friction to stop yourself. Hikers increase friction between their feet and the ground by wearing hiking shoes that grip the ground better. Tires on cars that create more friction make the car go faster, because instead of sliding, the tires grip the ground and push off.
Nothing. That's exactly what you want. When your coefficient of friction decreases too far, you need new tires.
When we would nail it, it would not be nailed,it would open because there is no friction.
It would not be able to move. The push of the engine driving the car forward depends on friction between the tyres and the road. If something else started it moving, the brakes couldn't work to stop it.
no
It would keep rolling.
They would hit the ground at the same time.
Friction is important in any movement. If you did not have friction between your feet and the ground, when you hit someone, you would slide away from them. Friction allows you to use the ground as a base to project power into your opponent.
ball will just move without rolling, staying in it's initial position but moving indefinitely (that is if it is given an initial force).
If there was no friction between the soles of your shoes and the sidewalk, you would be endlessly sliding down it until your momentum stopped you or you ran out of force.
Between ground and tires and between brake pads and moving surface.
You would need friction between the tires or tracks and the dirt the tractor is sitting. If you have extended legs, you need friction between the pads and the ground. You would want friction in the brakes. A clutch also relies on friction. Technically you could "dig water", but if you are trenching, then one needs friction between the dirt particles. It is also handy to have friction in your seat, steps, and controls.
A horse is able to jump because the friction between its hooves and the ground give it traction. Without this it would simply slide around.
You would increase friction so that you wouldn't slip, by using the brakes on your car of bike you increase friction to stop yourself. Hikers increase friction between their feet and the ground by wearing hiking shoes that grip the ground better. Tires on cars that create more friction make the car go faster, because instead of sliding, the tires grip the ground and push off.
If friction is more it leads to unwanted things
Without friction, the players would have trouble moving, as friction between their feet and the ground is part of what allows a person to walk or run. It would also be more difficult to make the ball start moving, or effectively catch it as friction helps grip the ball. It would also be more difficult to stop opposing players as friction between a tackler and the person being tackled is a large part of what allows the tackle to happen in many cases. Without friction, feet would simply slide along the ground rather then gripping it to propel a player forward or stop him, and the ball would be so slippery it would be nearly impossible to hold onto without completely cradling it.