1. Chapter 4 Forces in One Dimension

2. I. Force and Motion A.Force –push or pull exerted on an object. 1.Forces cause an object to: a.Speed up b.Slow down c.Change positions Which results in a change in… acceleration B. Force (F) is a vector –represents size (magnitude) and direction. 1.Force (F) – Just magnitude

3. object being manipulated System – Everything around the system External World – The hand & gravity are considered parts of the external world. II. Contact Forces and Field Forces A.Contact Force – An object from the external world makes contact with a system. Ex:holding a book pushing a book across a desk sitting in a chair B. Field Force – Forces that affect a system whether or not Earth is touching it. Ex:gravity magnetism

4. C. Agent – Cause of force applied to a system. Agent

5. III. Free-body Diagram System F Earth’s mass on the ball F rope on ball Contact with the external world A.Free-body diagram –Pictorial diagram that helps you identify all of the forces acting on a system

6. System F Earth’s mass on ball F hand on ball Contact with the external world

7. IV. Force & Acceleration A.What is the relationship between Force & Acceleration? 1.Units for Force = kg · m/s 2 = Newton (N)

8. V. Combining Forces A.Net Force –Resulting vector of combining forces. F 1 = 5 NF 2 = 5 N F net = 0 N

9. F 1 = 5 N F 2 = 10 N F net = 5 N

10. B. Newton’s Second Law – F = ma VI. Newton’s First Law A.An object at rest will remain at rest unless some unbalanced force acts on it. An object in motion will remain in motion unless some unbalanced force acts on it. 1. Newton’s first law is sometimes called the law of inertia. a. The tendency of an object to resist change.

11. Assignment: Practice Problems Pg. 89, questions 1 – 5 1. A flowerpot fall freely from a windowsill. (ignore any forces due to air resistance.) +y System F Earth’s mass on flowerpot vaF net