Help with frictional force concept

[Jetview]

Salutations everyone!

I'm sure this is a simple question for many of you, but I don't understand why doesn't the force of friction immediately stop an object after an applied force? And for an instance when an object is moving and eventually comes to a halt, was it because the force of friction increased or the applied force gradually decreased to a point the object is stopped by the bigger frictional force??

 

[bp_psy]

The kinetic friction force is determined by the normal to the contact surface and the kinetic friction coefficient.The friction is constant if the normal or contact surfaces do not change.If the kinetic friction force is greater then the other force on the object it will do negative work on the object until it stops.At that point we no longer talk about kinetic but by the static friction force which is now equal to the sum of the other forces on the object but smaller then the max fs.

 

[Lsos]

Force never stops an object "immediately". Force accelerates (or decelerates) an object at a certain rate, depending on its mass.

If there was no friction, the object would just keep on moving forever after we stop applying force to it. Because there is friction, the object slows down and eventually stops. But this always takes a finite time. Even if it looks immediate for some very light objects, it still takes a measurabe amount of time.

 

[tiny-tim]

Welcome to PF!

Salutations Jetview! Welcome to PF!

… why doesn't the force of friction immediately stop an object after an applied force? … or the applied force gradually decreased to a point the object is stopped by the bigger frictional force??

I think you're confused about applied forces.

When friction reduces something to a halt, there's usually no applied force …

with no force, it will carry on at the same speed forever (good ol' Newton's first law) …

the friction reduces its momentum slowly and steadily to zero.

If there is an applied force (eg from an engine), that applied forces is usually constant, and so is the friction, so the acceleration (which may be negative) is also constant.​

 

[PJC01]

Hello,

Thank you for reaching out for help with the concept of frictional force. Friction is a force that opposes the motion of an object and it is caused by the microscopic interactions between the surfaces of two objects. When an applied force is exerted on an object, the object will start to move. However, the force of friction acts in the opposite direction of the motion and it will resist the movement of the object. This means that the object will not stop immediately but will slow down and eventually come to a halt.

The reason for this is because the force of friction depends on the type of surfaces in contact, the force pushing the surfaces together, and the roughness of the surfaces. As the object moves, the surfaces are continuously in contact and the force of friction remains constant. However, as the object slows down, the applied force decreases while the frictional force remains the same. This results in the frictional force becoming larger than the applied force, causing the object to eventually come to a stop.

I hope this explanation helps you understand the concept of frictional force better. If you have any further questions, please don't hesitate to ask. Keep on learning!