Sliding friction, rolling friction, and fluid friction



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Unit 7A packet—Motion

Aristotle vs. Galileo Video- https://www.youtube.com/watch?v=2HR5UmG0q0s


  1. What did Aristotle say about falling objects?

  2. What did Galileo believe?

  3. How did he prove this?

  4. What was his INDEPENDENT VARIABLE?

  5. What did Galileo prove?


Apollo 15 proves Galileo (July 26, 1971, and ended on August 7)-- http://www.youtube.com/watch?v=03SPBXALJZI
BBC Video--Galileo

https://www.pinterest.com/pin/202662051958114939/


Choose a scientist to research and a creative project. Ideas for creative projects include: biography poster, scrapbook, movie poster, children’s book, biography bag, paper doll set.

Check pinterest for ideas.

My scientist is: _______________________________

My project idea is: ___________________________

List the websites you get information from here:

Have you ever played baseball or picked up a book? Activities as simple as walking your dog involve forces. A force is a push or a pull. A force may give an object energy or change its motion. Wind waves a flag on a flagpole. Engines run our cars. Electromagnetic forces bond ions together to form compounds. Forces even slow you down. The force that opposes the motion of an object is called friction. Friction is a force that brings an object to rest. When objects are in constant contact with each other, friction acts into a direction opposite of the motion of the moving object, slowing the object until it finally stops. There are 3 types of friction: Sliding friction, rolling friction, and fluid friction.



Sliding friction is when 2 solid surfaces slide past each other. When you move a chair across the floor, sliding friction opposes your motion. The amount of sliding friction depends on the weight of the object that is moving and the type of surface the object is sliding against. Rough surfaces apply more friction. A floor covered in carpet applies more friction than a tile floor. Rolling friction is when an object rolls over a surface. Wheels are examples of rolling friction. Rolling friction tends to oppose motion much less than sliding friction. This is why wheels are often used to move objects. Fluid friction is when objects move thorough fluids such as liquids or gases. The fall of a feather is opposed by air resistance. Fluid friction opposes motion even less than rolling friction. Lubricants can help reduce friction by changing sliding friction to fluid friction. Oil, grease, and wax are examples of lubricants. Friction is not always bad. You want friction to help your tires stop sliding on a wet road. Without friction, you could not walk. Think of how you easily you would be able to walk on an ice skating rink.

Imagine a sunrise. What is moving? The sun or the Earth? You could look at it both ways! The object or point from which movement is determined is called a frame of reference. The most common frame of reference is the earth itself. Movement can only be measured with reference to something that is assumed to be fixed in place, this is called relative motion. Examples:



  • The earth is moving around the sun at a rate of about 18 miles per second and is spinning at about 1000 miles per hour. Why don’t we feel like we are moving that fast?

  • If you are driving down the highway with your family and your mom tells you to “sit still”, can you do it?



  • Draw an example of frame of reference.

Speed and Velocity

A runner gets from one place to another because they moved or changed their position. Motion is a change in position relative to a frame of reference. Motion is measured by distance and time.

List 3 units to measure distance:

1.

2.



3.

List 3 units to measure time:









Motion is a change in position relative to a frame of reference. Motion is measured by distance and time. SPEED is the distance traveled by a moving object per unit of time the object traveled.


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