Friction.... Trouble understanding Friction?

Question

well i know that friction acts in the direction oposite to motion and eventually causes an object to come to a stop. So how does it cause an automobile to start moving if it acts in the opposes the direction of the wheels of the car?
why does a car not move on ice when there is no friction, shouldn't it move? very confused thanx to the people who help

Answer 1

There are 2 types of friction: kinetic and static
Kinetic friction slows a sliding object to a stop.
Static friction prevents a stationary object from moving. It is usually much stronger than kenitic friction. (That's why it is tough to get a heavy, stationary cardboard box to slide on the carpet, but once it's moving, it becomes easier)

With your automobile example, the tires on the car roll on the ground. It's important to note that they roll... not slide, because sliding object experience kinetic friction forces, while rolling objects experience static friction forces. (This is why you get a carpet burn if you slide on the carpet, but not if you roll).
Static friction prevents the tire from "Sliding" on the road, even though the axle of the car is forcing it to rotate. The tire applies a "horizonal" force on the road, attempting to slide (and squeel), but the road applies an equal and opposite static frictional force. The result is a "roll".

If for some reason, the you slam on the breaks and the breaking force applied to the tire exceeds the maximum static friction force between the road and the tire, the tire will slide (skid). The resulting kentic frictional force stopping the car is much smaller than the previous static frictional force stopping the car. As a result, skidding cars slow down less rapidly than reglar breaking cars. This is why anti-lock breaks were invented - to keep cars from skidding in a stop.

I really hope this helps. Tried to keep it short and sweet.

Answer 2

Friction is a force and it causes retardation to a moving body.So if the velocity of the car is more than the force of friction,friction itself cannot stop the car,you have to apply the brake and the brakes adds up the friction and finally stops the car.But if you roll a ball on the ground,it automatically stops after some distance beause it does not have an engine attached to it to apply force to it..and so the ball slows down more and more and finally its velocity becomes zero and it comes to a stop.To think that ice has got no friction is completely wrong but the fat is that it has got very less friction.in fact polished surfce has less friction but w cannot imagine any surface without nil friction.Even air has friction but a minimum one.That is why airplanes can run at very high sped.polished roads have less friction than rough roads and so you are able to drived car fastr on a polished road.
i hope I have been able to rmove your misconception to some extent.

Answer 3

You first need to understand Newton's 3rd law of motion which states: "For every action there is an equal and opposite reaction". Since the friction is in the opposing direction of the car, friction is required for the car to move forward, or else Newton's 3rd law will not hold.