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Unit 2 Chapter 5: Forces

Unit 2 Chapter 5: Forces. Ms. Brown 8 th Grade General Science. What causes forces?: A force is a push or pull , or an action that has the ability to change motion. Forces can increase or decrease the speed of a moving object.

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Unit 2 Chapter 5: Forces

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  1. Unit 2Chapter 5:Forces Ms. Brown 8th Grade General Science

  2. What causes forces?: • A force is a push or pull, or an action that has the ability to change motion. • Forces can increase or decrease the speed of a moving object. • Forces can also change the direction in which an object is moving.

  3. How are forces created? • Forces are created in many ways. • For example, your muscles create force when you swing a baseball bat.

  4. What kind of forces are there? • Elemental forces: • *Make up all the forces in the universe* • Electromagnetic forces are important to technology. • Gravity is a universal force.

  5. What units do we use for Force? • The pound is a unit of force commonly used in the United States. • For smaller amounts, pounds are divided into ounces (oz.). • There are 16 ounces in 1 pound.

  6. When you measure weight in pounds, you are measuring the force of gravity acting on an object.

  7. Although we use pounds all the time in our everyday life, scientists prefer to measure forces in newtons. • The Newton (N)is the metric unit of force. • The Newton is a smaller unit of force than the pound (lb).

  8. How do we measure forces? • When solving problems ~ Use a force vector

  9. The arrow points in the direction of the force. *Remember your coordinate plane* + N - + W - E S

  10. Drawing Vectors: • The x- and y-axes show the strength of the force in the x and y directions. • When drawing a force vector to show its strength, you must also choose a scale.

  11. How do forces act? • One way forces act is the result of direct contact. • A contact force is transmitted by matter directly touching other matter such as wind acting to slow a parachute.

  12. Another way forces act is by • force fields. • The force of gravity between Earth and Moon appears to be what people once called “action at-a-distance”. • Today we know that the gravitational force is carried from the Earth to the Moon by a force field.

  13. Classify These forces as contact forces or the result of force fields:

  14. Contact forces from ropes and springs: Ropes and strings are often used to make and apply forces. Ropes are used to transfer forces or change their direction. The pulling force carried by a rope is called tension. Tension always acts along the direction of the rope.

  15. What are the 2 categories of forces?: galaxy M100 about 50 million light years from Earth

  16. How do we calculate weight?: • W = m x g • Weight (N) = mass (kg) x gravity (N/kg) • ~ See Sample Problem • (Pg. 105 in textbook)

  17. Sample Question~ From Previous NJ Ask 8 Exam: Louise is pushing a basket of apples:  What are two things Louise could change to make it easier to push the basket?  What is one change that would make it harder to push the basket?  Louise could 1. remove some apples 2. get a friend to help 3. push with greater force  Push the basket uphill, add more apples, push over a rough surface

  18. http://vimeo.com/4889504 FORCE Song VIDEO:

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