Friction

1. Friction Describe effects of friction on moving objects

2. Background knowledge When a force, a push or pull, is applied to an object, the object speeds up, slows down, or goes in another direction. A relationship exists between the strength of a force and its effect on the object. Inertia is the physical property used to describe how difficult it is to move a stationary object or to stop a moving object.

3. Background knowledge Mass- the measure of the amount of matter in an object. The larger the mass, the bigger the object. The greater the mass of the object, the more inertia it has, thus the harder it is to move an object or stop the object once in motion. Any mass in motion has momentum. Any two objects with mass attract each other with gravitational force. video segment (inertia) http://app.discoveryeducation.com/search (Demonstrations of inertia) http://app.discoveryeducation.com/search

4. Friction is a force that makes it difficult for an object to move across a surface. The amount of friction depends on the surface type and how hard the surfaces are pressed together. Everyday life provides examples of how friction both helps and hinders everything we do. Video segment: http://app.discoveryeducation.com/search

5. Effects of friction include: • Production of heart when objects, such as hands and sticks are rubbed together. • Friction causes a meteor traveling through the atmosphere to glow. • Substances with smooth surfaces, including oil, water, ice, and glass, can reproduce the effects of friction on moving objects. • Generally, less friction results in an increase of an objects motion (momentum). • More friction slows an objects motion.

6. Vocabulary Friction- is a force that makes it difficult for an object to move across a surface. A force that slows or stops motion. Resistance- Momentum- means motion Video segment: (momentum) http://app.discoveryeducation.com/search

7. Vocabulary Inertia- a physical property used to describe how difficult it is to move an object or to stop when that is moving. Gravitational force- a force that pulls things to the ground. Speed- the magnitude of the rate of change of an objects position. Force- a push or a pull

8. Vocabulary Balanced forces-when forces are equally balanced on both sides Lubricant- a substance that can reduce friction. Increase- to go up Decrease- to go down Force- a push or pull to an object

9. Things to know! Balanced forces are those that press equally on opposite sides of an object and result in no movement. A push or pull is the result of unbalanced forces. Momentum is determined by the mass and velocity of the object as well as the surface angel. A bicycle traveling uphill will have less momentum than a bicycle traveling downhill.

10. Things to know! Inertia is the tendency for an object to remain at rest until force causes a change. Inertia explains why rocks fall off backs of wagons when the wagon is jerked forward. Inertia is also the tendency of objects that are in motion to remain in motion such as your body jerking forward when a car makes a sudden stop or when a sharp turn changes the direction of the movement.

11. Things to know! Friction can be increased or decreased. Surfaces materials that affect friction: rough surfaces such as carpet, gravel and sandpaper increase the amount of friction between objects and smooth surfaces such as glass, ice, and dew decrease the friction. Lubricants are substances that reduce friction. Example of lubricants include oil, water, and ice.