Kinds of Friction

Kinds of Friction Physical Science 2023 Name: ________________________________________________ Period: _______ Date: ___________ Abigayle Vasquez Essential Question: How do I classify frictional forces into one of four types: static, sliding, rolling, and fluid ? Fric Friction is a force that objects have which makes them resist motion or movement across or against one another. If one object with a flat surface is placed on top of another, the top object can be lifted without any act of resisting except that of gravity. If one object is pushed or pulled over another, there is an act of resistance that is caused by friction. If one object moves over a stationary object, the stationary object will slow down the moving object. If a force tries to move an object at rest on a surface, the surface resists this motion with an opposing force of friction. The size or amount of the frictional force depends on the kind of surfaces which are rubbing together. Friction can be used for many important things such as helping the wheels of a train stay on the rails of the track. It also allows a mechanical device that carries things from one place to another also known as a conveyer; it helps the belt of a conveyor stay on pulleys without slipping. We need friction to walk; if we did not have any friction, everything would be slipping and sliding away. That is why we can't walk on ice very well; the ice is so smooth and flat that it produces less friction than a sidewalk, making it hard to walk on ice. Friction occurs any time when two objects or surfaces are rubbed together. The more the pressure on the objects when they are rubbed together, the more friction. If you are trying to slow down, friction works with you, but when you try to speed up, friction works against you. Different methods can be used to reduce the amount of friction between the surfaces of the objects in contact. One way to reduce friction is to apply a lubricant to the surfaces, another is to use casters, rollers, or ball bearings between the surfaces, and another is to smooth the surfaces of the objects in contact. Different kinds of motion give rise to different types of friction between objects. Static friction occurs between stationary objects, while sliding friction occurs between objects as they slide against each other. Other types of friction include rolling friction and fluid friction. Static friction prevents an object from moving against a surface. It is the force that keeps a book from sliding off a desk, even when the desk is slightly tilted, and that allows you to pick up an object without the object slipping through your fingers. In order to move something, you must first overcome the force of static friction between the object and the surface on which it is resting. This force depends on the coefficient of static friction (µs) between the object and the surface and the normal force (N) of the object. A book sliding off a desk or brakes slowing down a wheel are both examples of sliding friction, also called kinetic friction. Sliding friction acts in the direction opposite the direction of motion. It prevents the book or wheel from moving as fast as it would without friction. When sliding friction is acting, another force must be present to keep an object moving. In the case of a book sliding off a desk, this force is gravity. Rolling friction hinders the motion of an object rolling along a surface. Rolling friction slows down a ball rolling on a basketball court or softball field, and it slows down the motion of a tire rolling along the ground. Another force must be present to keep an object rolling. For example, a pedaling bicyclist provides the force necessary to the keep a bike in motion. Objects moving through a fluid experience fluid friction, or drag. Drag acts between the object and the fluid and hinders the motion of the object. The force of drag depends upon the object’s shape, material, and speed, as well as the fluid’s viscosity. Viscosity is a measure of a fluid’s resistance to flow. It results from the friction that occurs between the fluid’s molecules, and it differs depending on the type of fluid. Drag slows down airplanes flying through the air and fish swimming through water. An airplane’s engines help it overcome drag and travel forward, while a fish uses its muscles to overcome drag and swim. Calculating the force of drag is much more Clarifying Questions: 1. What is the force that makes object resist motion? The force that makes an object resist motion is friction. 2. What is the force that resist motion when lifting an object? Explain. When lifting an object, the force that resists motion is primarily due to static friction. This is because the object is initially at rest, and static friction opposes the applied force until the object starts moving. 3. what does a stationary object do to a moving object? A stationary object exerts static friction on a moving object, which resists the motion of the moving object until it overcomes the force of static friction. _______________________________________________________________________________________ factors such as the nature of the surfaces in contact, 4. The size or amount of frictional force depends on ____________________________________________ the force pressing the surfaces together, and any lubrication present. _______________________________________________________________________________________ 5. How does friction help trains work? Friction helps trains work by providing the necessary traction between the wheels and the tracks, allowing the train to move ___________________________________________________________________________________________ forward without slipping. _______________________________________________________________________________________ 6. Why do we need friction to walk? We need friction to walk because it provides the necessary grip between our shoes and the ground, preventing ___________________________________________________________________________________________ slipping and allowing us to push off the ground with each step. _______________________________________________________________________________________ 7. When does friction occur or happen? Friction occurs whenever two surfaces come into contact and attempt to move relative to each other. _______________________________________________________________________________________ _______________________________________________________________________________________ 8. How is friction increased? Read and Think! Friction can be increased by increasing the force pressing the surfaces together or by increasing _______________________________________________________________________________________ the roughness of the surfaces. _______________________________________________________________________________________ 9. How is friction reduced? Read and Think! Friction can be reduced by using lubricants or by making the surfaces smoother. ___________________________________________________________________________________________ _______________________________________________________________________________________ 10. What are the four kinds of friction? The four kinds of friction are static friction, kinetic friction, rolling friction, and fluid friction. ___________________________________________________________________________________________ _______________________________________________________________________________________ 11. What must you overcome first before you can move an object? Before you can move an object, you must overcome static friction, which is the force resisting ___________________________________________________________________________________________ the initial motion of the object. _______________________________________________________________________________________ 12. What is another name for sliding friction? Another name for sliding friction is kinetic friction. _______________________________________________________________________________________ _______________________________________________________________________________________ 13. What is the direction of a sliding friction? The direction of sliding friction opposes the direction of the motion of the object. _______________________________________________________________________________________ _______________________________________________________________________________________ 14. What does rolling friction do to the motion of a rolling ball? Rolling friction slows down the motion of a rolling ball by resisting its rolling motion, causing it to gradually _______________________________________________________________________________________ come to a stop. _______________________________________________________________________________________ 15. What hinders the motion of an object on liquid and gas ( fluid )? Fluid friction, or drag, hinders the motion of an object on liquid and gas by exerting a resistance force against ___________________________________________________________________________________________ the object's motion through the fluid medium. _______________________________________________________________________________________ factors such as the speed of the object, 16. The amount of fluid friction or drag depends on _____________________________________________ the shape of the object, the density of the fluid, and the viscosity of the fluid. _______________________________________________________________________________________ _______________________________________________________________________________________ 17. What is aerodynamics? ( Research) think! You see this in cars, airplanes, helmets etc. Aerodynamics is the study of how air moves around objects, particularly in relation to the design and performance of vehicles, structures, and equipment. It involves understanding the forces acting on objects as they move through the air and optimizing their design to minimize drag and maximize efficiency. Examples of applications include designing streamlined cars, airplanes, helmets, and other objects to reduce air resistance and improve performance.