Forces and Free Body Diagrams 12314 Contact Forces

Forces and Free Body Diagrams 12/3/14

Contact Forces n Applied Force n Surface Force n Friction Force n Air Resistance Force n Tension Force n Lift Force n Thrust Force Action-at-a-Distance Forces n Force of Gravity n Electrical Force n Magnetic Force

Types of Forces Name of Force Symbol Force of Gravity Fg ← Fgrav Applied Force Fapp Description of the force. The force with which the earth or other massively large object attracts another object towards itself. Is always directed downwards A force which is applied to an object by a person or another object.

Types of Forces Name of Force Symbol Description of the force. Surface Force & Fsurf ← Normal Force FNorm (Normal means FN perpendicular) The support force exerted upon an object which is in contact with a surface of another object. Friction Force The force exerted by a surface as an object moves across it or makes an effort to move across it. Directed opposite of motion. Ff ← Ffric

Types of Forces Name of Force Symbol Description of the force. Air Resistance Force Fair Tension Force FT ← Ften A frictional force which acts upon objects as they travel through the air. Directed opposite of motion. The force which is transmitted through a string, rope, cable, or wire (bridge deck) when it is pulled.

Types of Forces Name of Force Symbol Description of the force. Lift Force Flift Thrust Force Fthrust A force that directly opposes the weight of an “aircraft”. The force that moves an “aircraft” though the air.

Free Body Diagrams n Free-body diagrams (F. B. D. ): Diagrams that show the relative magnitude and direction of all forces acting upon an object in a given situation.

Free Body Diagrams n n n The direction of the arrow shows the direction that the force is acting. The size of the arrow in a free-body diagram reflects the magnitude of the force. Each force is labeled to indicate the type of force. Represent the object by a box (or drawing) and draw the force arrows from the center of the box outward in the direction that the force is acting. There can be any number of forces

Forces on a Wing

Free Body Diagram of a Wing

Examples of F. B. D. n n n Ex 1) Mr. Z. standing on the ground. Ex 2) As Mr. Z. is throwing a racquet ball across the room to the left. Ex 3) The racquet ball as it moves through the air after Mr. Z. has thrown it.

Homework Due on Friday 12/5/14 n 3 rd Law Practice with F. B. D. (1 - 4 and 12) n Free Body Diagrams Practice

Free Body Diagram Activities 11/6/13

Free Body Diagrams n n “Free Body Diagram Activities” – Due tomorrow Thurs. 11/7/13 “Free Body Diagram Practice” – Due Friday 11/8/13

Free Body Diagram Activities 1) Sliding a book across the table to the right. A) Before you slide the book. B) Sliding the book as it accelerates C) Sliding the book with constant velocity. 2) Lightly kicking a tennis ball across the floor to the right. A) As you are kicking the ball. B) As the ball is rolling across the floor after the kick. C) When the ball comes to a complete stop. 3) Throwing a tennis ball straight up into the air. A) As you are throwing the ball in your hand. B) When the ball is going up. C) When the ball is coming down. D) When you catch the ball. 4) Throwing a paper airplane to the right. A) When you are throwing the paper airplane. B) When the paper airplane is in the air. C) As the paper airplane hits the ground. 5) The foot of a person walking to the right then stopping. A) Before the person starts walking. B) As the person is walking. C) As the person stops.

Free Body Diagrams