Forces and Free Body Diagrams 11/6/13

Bellwork What book did Newton write in 1687? What book did Newton write in 1687? The Principia (Mathematical Principles of Natural Philosophy) The Principia (Mathematical Principles of Natural Philosophy)

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

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

Types of Forces Name of Force Symbol Description of the force. Force of Gravity F g ← F grav The force with which the earth or other massively large object attracts another object towards itself. Is always directed downwards Applied Force F app 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 & Normal Force (Normal means perpendicular) F surf ← F Norm F N The support force exerted upon an object which is in contact with a surface of another object. Friction Force F f ← F fric The force exerted by a surface as an object moves across it or makes an effort to move across it. Directed opposite of motion.

Types of Forces Name of Force Symbol Description of the force. Air Resistance Force F air A frictional force which acts upon objects as they travel through the air. Directed opposite of motion. Tension Force F ten 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. Compression Force F comp A force that acts to compress or shorten the object it is acting on. Lift Force F lift A force that directly opposes the weight of an “aircraft”. Thrust Force F thrust The force that moves an “aircraft” though the air.

Free Body Diagrams The direction of the arrow shows the direction that the force is acting. 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. The size of the arrow in a free-body diagram reflects the magnitude of the force. Each force is labeled to indicate the exact type of force. Each force is labeled to indicate the exact 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. 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. Can be any number of forces Can be any number of forces

Forces on a Wing

Free Body Diagram of a Wing

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

Free Body Diagram Activities 11/6/13

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