Downloaded 136 times
Uploaded byClement Tay
Diagrams and Friction
This document discusses representation in physics, specifically focusing on free-body diagrams. It defines what a free-body diagram is and provides examples of drawing them to represent different forces like weight, tension, and contact forces. Key examples include a person standing, a hanging picture, and boats being towed. The document also discusses the effects of friction, like how it allows cars and feet to move forward, and the factors that influence the amount of friction between surfaces.
In this document
Powered by AI
Introduction to representation through free-body diagrams, definitions, formulas, and language of physics.
Outcomes include identifying forces, drawing free-body diagrams, and applying F=ma.
Explains free-body diagrams, illustrating forces like weight and contact force on an object.
Discusses action-reaction force pairs and demonstrates free-body diagrams of different bodies.
Examples involving a gymnast, two boxes, and analyzing forces includes tension in free-body diagrams.
Analyzing lift problems such as at rest, accelerating upwards, constant velocity, and accelerating downwards.
Recap of vector diagrams, including unbalanced and balanced forces, and their implications.
Illustrates balanced and unbalanced forces through real-life scenarios like a picture on a wall and a moving boat.
Discusses the nature of friction, effects on motion, examples of air resistance and lorries, and factors affecting friction.
Final summary of key concepts of forces, free-body diagrams, and friction.
More Related Content
Similar to Diagrams and Friction
Diagrams and Friction
- 1.
- 2. WHAT IS REPRESENTATION? DefinitionsFormulas Diagrams Graphs Language of Physics
- 3. LEARNING OUTCOMES Identifyforces acting on an object and draw free-body diagrams Solve problems for a static-point mass Recall and apply the equation F = ma to new situation or to solve related problems
- 4. FREE-BODY DIAGRAMS Adiagram which shows all the forces acting on a body Consists primarily of a sketch of a body and arrows representing the forces acting on it Weight Contact force Tension
- 5.
- 6. WEIGHT Weight ofa body is the gravitational force exerted by the Earth on the body. The weight acts at the center of gravity of a body. It is always directed towards the center of the Earth The free-body diagram of a body falling without air resistance is shown below
- 7. CONTACT FORCE Contactforce is the force exerted by the contact surface on the body Acts perpendicularly to the contact surface Two forces act on the body: they are the contact force and the weight
- 8. RECALL: WEIGHT VS. CONTACTFORCE Contact forces are forces that act on a body at the point of contact between two different bodies Non-contact forces is a force that acts on a body such as the weight which acts through the center of gravity (CG) of an object Contact forces Non-Contact forces
- 9. WHAT ARE THEFORCES ACTING ON THE BODIES? The pair of action and reaction forces is the gravitational force by the Earth on the man and the gravitational force by the man on the Earth There are 2 free- body diagrams : One for the man and the other for the Earth
- 10. FREE-BODY DIAGRAM Thefree-body diagram of the man shows the force acting on him only The free-body diagram for the Earth shows the force that acts on the Earth only
- 11. WHAT ARE THEFORCES ACTING ON THE BODIES? The first pair of action and reaction forces is the gravitational force by the Earth on the man and the gravitational force by the man on the Earth The second pair of action and reaction forces is the contact force by the man on the Earth and the contact force by the Earth on the man
- 12. FREE-BODY DIAGRAM Thefree-body diagram shows two forces : F1 and F2 acting on the man. Since the man is at rest , the two forces are equal and opposite in direction
- 13. FREE-BODY DIAGRAM Thefree-body diagram for the Earth shows two forces , F1 and F2 acting on the Earth Since F1 = F2 , the Earth is also at rest
- 14. THINK! Which areaction-reaction pairs?
- 15. WORKED EXAMPLES Gymnast 2 boxes Lift
- 16. GYMNAST How manyfree bodies? How many action- reaction pairs? What are the forces acting on each body?
- 17.
- 18.
- 19.
- 20. TENSION The tensionis directed along the length of the string and pulls equally on the support and the pendulum bob The diagram below is not a free-body diagram as it shows forces acting on three bodies: the pendulum bob, the string and the support. It will not be useful in analysis.
- 21. TENSION Isolate thependulum bob as a free-body Only contact force acting on the bob is the tension Free-body diagram of the pendulum bob consists of the tension and weight only
- 22. PUTTING IT TOGETHER Weight and contact force are equal. No resultant force acting vertically Acceleration of the crate is due entirely to the tension force
- 23.
- 24.
- 25. IN A LIFT– DAILY EXPERIENCES (VIDEO)
- 26. LIFT PROBLEM –AT REST
- 27. LIFT PROBLEM –ACCELERATING UPWARDS
- 28. LIFT PROBLEM –CONSTANT VELOCITY
- 29. LIFT PROBLEM –ACCELERATING DOWNWARDS
- 30.
- 31. VECTOR DIAGRAMS 2scenarios Unbalanced forces Balanced forces
- 32. UNBALANCED FORCES When 3forces are applied to a point of an object , the resultant force (due to it being unbalanced) acting on the object can be obtained by adding the force vectors Vectors A,B and C represent three forces
- 33.
- 34. BALANCED FORCES • When3 forces acting on an object is balanced , resultant force is ________. • There is no _________. • An object will either ________ or ____________.
- 35. BALANCED FORCES Considera picture hanging on the wall. What are the forces acting on the picture frame?
- 36.
- 37. VECTOR DIAGRAM – BALANCEDFORCES Weight Tension Tension Tension Tension Weight
- 38. UNBALANCED FORCES Considera boat being towed by 2 other boats. TensionTension Boat Tension Tension Resultant Force
- 39. COMPARE: Picture on wall (Balancedforces) Moving boat (Unbalanced forces) Tension Tension Weight Tension Tension Resultant Force
- 40.
- 41.
- 42.
- 43. LEARNING OUTCOMES Explainthe effects of friction on the motion of a body
- 44.
- 45.
- 46.
- 47.
- 48. EFFECTS OF FRICTIONON MOTION As a useful force To move forward, you place one foot in front of you and push your other foot backwards on the ground. The friction between your shoe and the ground prevents you from slipping.
- 49. EFFECTS OF FRICTIONON MOTION As each wheel turns, friction is created at the point of contact between the wheel and the road At the point of contact, the wheel is moving backwards Friction acts in the opposite direction and provides the forward force that drives the car
- 50. WHEN THERE ISNO FRICTION Without friction, the wheels would spin without helping the car to move forward. An example of this is when a car gets stuck in mud or fine sand as shown above
- 51. FACTORS THAT AFFECT FRICTION Depends on the nature of the surfaces in contact The rougher the surface the greater is the friction Is proportional to the force pressing the surfaces together (in the case of horizontal movement, the pressing force is the weight). Pushing heavy vs. light objects • Is independent of the area of contact
- 52.