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Types of Forces Free Body Diagrams.

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Presentation on theme: "Types of Forces Free Body Diagrams."— Presentation transcript:

1 Types of Forces Free Body Diagrams

2 Force Push or pull The cause of an acceleration or the change in an object’s velocity (pg. 124)

3 Force can act through contact or distance (pg. 125)
Contact force- force that arises from the physical contact of two objects Ex: pulling a spring, pull a wagon, pushing car Field force- force that can exist between objects, even in the absence of physical contact between the objects Ex: gravity, electrical charges

4 Applied Force Force which is applied to an object by a person or another object Fapp: student pushing or pulling a desk across the room

5 Gravity Force Force with which the earth, moon, or other massively large object attracts another object towards itself. (By definition, this is the weight of the object) Fgrav: = mass x acceleration due to gravity Where acceleration due to gravity is 9.8 m/s2

6 Normal Force The support force exerted upon an object which is in contact with another stable object. Ex: book resting on a table, the table is exerting an upward force upon the book in order to support the weight of the book Fnorm

7 Friction Force The force exerted by a surface as an object moves across it or makes an effort to move across it Ffrict = (“mu”) (fnorm) Sliding and static friction

8 Air Resistance Force Force which acts upon objects as they travel through air (often observed to oppose the motion of an object) Fair : skydiver, or downhill skier

9 Tension Force Force which is transmitted through a string, rope, cable or wire when it is pulled tight by forces acting from opposite ends. Ftens:

10 Spring Force Force exerted by a compressed or stretched spring upon any object which is attached to it. Fspring:

11 Coefficient of Friction
The 'coefficient of friction' (COF), symbolized by the Greek letter µ “mu”, is a dimensionless scalar value which describes the ratio of the force of friction between two bodies and the force pressing them together. The coefficient of friction depends on the materials used; for example, ice on steel has a low coefficient of friction, while rubber on pavement has a high coefficient of friction. Coefficients of friction range from near zero to greater than one – under good conditions, a tire on concrete may have a coefficient of friction of 1.7 “mu” =coefficient of friction

12 Problem 1 A book is at rest on a table top. Draw the free body diagram that depicts this action.

13 Problem 2 An egg is free-falling from a nest in a tree. Neglect air resistance. Draw a free-body diagram showing the forces involved

14 Problem 3 A flying squirrel is gliding (no wing flaps) from a tree to the ground at constant velocity. Consider air resistance. A free body diagram for this situation looks like…

15 Problem 4 A rightward force is applied to a book in order to move it across a desk. Consider frictional forces. Neglect air resistance. Construct a free-body diagram. Let’s see what this one looks like.

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