1 / 45

WHAT IS A FORCE?

WHAT IS A FORCE?. A force is a push or a pull, and one body exerts a force on another SI units are Newton (N), 1N=1kg x m/s 2. Effects of forces on objects. Balanced forces – forces are equal in size & opposite in direction Net force – force that changes the velocity of the object

echesney
Download Presentation

WHAT IS A FORCE?

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. WHAT IS A FORCE? • A force is a push or a pull, and one body exerts a force on another • SI units are Newton (N), 1N=1kg x m/s2

  2. Effects of forces on objects • Balanced forces – forces are equal in size & opposite in direction • Net force – force that changes the velocity of the object • Object accelerates in the direction of the greater force

  3. Friction • A force that opposes motion between two surfaces that are touching each other • Amount of friction depends on 2 factors • the kinds of surfaces • the force pressing the surfaces together

  4. Four types of Friction • Static friction: force that acts on objects that are NOT moving, acts in direction OPPOSITE to that of the applied force • Sliding friction: force that opposes the direction of motion of an object as it slides over a surface (less than static)

  5. Four types of Friction • Rolling friction: force that acts on rolling objects (less than static or sliding) • Fluid friction: opposes motion of an object through a liquid or gas

  6. Gravitational Force • Gravity – the attracting force exerted by every object on every other object • Amount of gravitational force between objects depends on 2 things…

  7. Gravitational Force 1)-mass a) more mass=more g force b) less mass=less g force 2)-distance a) greater distance=less g force b) lesser distance=more g force

  8. ACCELERATION DUE TO GRAVITY Falling objects accelerate at 9.8 m/s2 *same for ALL objects (in a vacuum with no air resistance) This means that for each second the body is falling, its velocity increases by 9.8 m per s 

  9. Air Resistance • The force that air exerts on a moving object • Amount of air resistance depends on: • Speed 2. Size 3. Shape 4. Density

  10. Terminal Velocity • The highest velocity that will be reached by a falling object • Downward force of gravity equals the upward force of air resistance

  11. Projectiles • Anything shot/thrown through the air • A thrown ball has constant horizontal velocity • Gravity pulls the ball downward • Vertical acceleration increases, changing the direction of the projectile to forward and downward

  12. Constant horizontal velocity

  13. Circles Centripetal Acceleration: towards the center of a curved or circular path

  14. Circles Centripetal Force exerted toward the center of a curved path; without this force object will shoot off in a straight line in the direction it was traveling

  15. Newton’s 1st Law • States that an object moving at a constant velocity keeps moving at that velocity unless a net force acts on it. If an object is at rest, it stays in rest unless a net force acts on it. • “If I push it, it goes” • Also called the law of inertia

  16. Inertia • Tendency of an object to resist any change in its motion • If an object is moving, it keeps moving at that speed and direction unless a force acts on it. • If an object is at rest, it stays at rest unless a force acts on it (velocity at rest = 0m/s)

  17. Inertia • The more mass an object has, the greater its inertia • More force would be needed to change the velocity of the object w/ greater inertia (which also means greater mass)

  18. Newton’s 2nd Law • The acceleration of an object is equal to the net force acting on it divided by the object’s mass, a=F/m or simply F=ma • The amount of acceleration is affected by • size of the force • mass of the object

  19. Weight • The measure of the force of gravity on an object Fg=W=mg measured in Newtons (N) 2. 1kg=9.8N (1N=0.22 pounds) 2.156lb = 1.0 kg http://resources.yesican-science.ca/trek/mars2/final2/notes/new_notes.html Weight or Force due to gravity Acceln due to gravity mass

  20. Mass • The amount of matter in an object constant independent of location • measured in grams (g) and kilograms (kg) **Find your mass in kg then your weight in Newtons.

  21. Momentum • More mass = More momentum • More velocity = More momentum • Momentum is transferred

  22. Law of conservation of Momentum • In a closed system, the loss of momentum of one objects equals the gain in momentum of another object – momentum is CONSERVED

  23. Problem Review Activity • Each person will be assigned a color (yellow, orange, or red) • On notebook paper, you will solve the problems only for the color you are assigned • To receive full credit, you must… • 1. Write down your “givens” (v = 3m/s, etc.) • 2. Show your work to solve the problem • 3. Put a box around your answer • 4. Write all units!

  24. Please add the following questions to the end of your test… • 31. Calculate the acceleration of a car that accelerated from 5 m/s to 10 m/s in 2 s. • 32. Calculate the acceleration of a car that slowed down from 10 m/s to 5 m/s in 2 s. • 33. Calculate the momentum of a 12 kg object traveling at a velocity of 6 m/s. • 34. Name one thing you have enjoyed about physical science so far. • 35. Name one activity you wish we did more of in physical science.

  25. PhysiFacts 5.4 4/30 • 13. What is the velocity of a car that covered 20km in 2 hours? • 14. What is the acceleration of an object that accelerated from 5m/s to 10m/s in 2 seconds? • 15. How much force needs to be applied to an 5km object to accelerate it at a rate of 2m/s2? • 16. Calculate the momentum of a 3kg object moving at a rate of 3m/s.

  26. Force and Motion Review • To review before test corrections… • Each table will be assigned a topic • Using the chalk markers, you will create a review “poster” on the surface of your tables • You will have 15 minutes to design before groups will rotate around the room to see each “poster” • Test corrections will follow this activity

  27. Review Topic Assignments • Group 1: Newton’s Laws • Group 2: Velocity and Acceleration • Group 3: Momentum and Force equations • Group 4: Vocabulary Review • Group 5: Distance – Time Graphs and Speed – Time Graphs

  28. Group ____: Newton’s Laws • Write out each one of Newton’s three laws of motion • Draw a picture for each law • Define inertia • If something has more mass, does it have more inertia?

  29. Group ____: Velocity &Acceleration • Define velocity • Write the equation & the circle for velocity • Define all units for velocity • Solve 3 practice problems and SHOW WORK! • Define acceleration • Write the equation for acceleration • Define all units • Solve 1 practice problem and SHOW WORK!

  30. Group ____: Momentum & Force • Define force • Write the equation and the circle for force • Define all units for the force equation • Solve three practice problems and SHOW WORK! • Define momentum • Write the equation and the circle for momentum • Define all units for the force equation • Solve three practice problems and SHOW WORK!

  31. Group ____: Vocabulary ReviewInclude the following terms and choose 5 to draw a picture for • Terminal velocity • Velocity • Acceleration • Momentum • Force • Friction • Net force • Balanced force • Static Friction • Fluid Friction • Sliding Friction • Rolling Friction

  32. Group _____: The Graphs • Distance-Time Graph • Draw an example and label the x-axis and y-axis • What does the slope tell you? • What does a horizontal slope tell you? • Speed-Time Graph • Draw an example and label the x-axis and y-axis • What does the slope tell you? • What does a horizontal slope tell you?

  33. PhysiFacts 5.1 4/18 • 1. A car increases it’s velocity from 0 m/s to 14 m/s in 2 seconds. Solve for acceleration. • 2. How long will your trip take (in hours) if you travel 350 km at an average speed of 80 km/hr? • 3. A racing car’s velocity is increased from 44 m/s to 66m/s in 11 seconds. Solve for acceleration.

  34. Chapter 11 Assessment – p. 350-351 • Will count as a quiz grade! • 1-10 – just write the letter answer • Draw the concept map and fill it in

  35. IAN pg. 29: Types of Friction • Define FRICTION • List the two factors that determine the amount of friction • Draw a box with four sections for each of the four types of friction: static, sliding, rolling, fluid • Define and draw a picture for each type of friction

  36. Agenda: 4/19 • Place cell phone in a pouch – you do not need a calculator today! • Be in your seat and ready to start when the bell rings! • Today’s Order of Operations: • PhysiFacts • Motion Video • Defining Motion IAN page 30 • Vocab Review Game • End of the grading period is April 24! • IAN pages 21-30 due FRIDAY APRIL 27!

  37. PhysiFacts 5.2 4/19 • 4. Name the four types of friction. • 5. A push or pull that one body exerts on another = • 6. Newton’s First Law: • 7. Newton’s Second Law: • 8. Newton’s Third Law:

  38. Agenda: 4/23 • Place cell phone in a pouch – you DO NOT need a calculator today! • Sit in groups of FOUR and get out your notes! • Be in your seat and ready to start when the bell rings! • Today’s Order of Operations: • PhysiFacts • IAN page 31: Newton’s Laws of Motion • Ping Pong Soccer Lab • TIME FOR MAKE UP WORK! • Reminders: end of grading period is TOMORROW!

  39. PhysiFacts 5.3 4/23 • 9. The amount of gravitational force depends on… (2 things) • 10. Forces equal in size and opposite in direction = • 11. SI unit for force = • 12. The highest velocity that will be reached by a falling object

  40. IAN page 31: Newton’s Laws of Motion • Newton’s First Law • What does the law state? • What is another name for this law? • Define inertia. • Newton’s Second Law • What does the law state? • What is the equation associated with this law? • Newton’s Third Law • What does this law state? • DRAW AN ILLUSTRATION FOR EACH LAW!

  41. Agenda: 4/24 • Keep cell phone today! • Turn in any labs from yesterday! • Be in your seat and ready to start when the bell rings! • Today’s Order of Operations: • Paper Airplane Lab • Time for make up work including Ch. 12 guided outline! • Reminders: end of the grading period is TODAY!, Forces and Motion Test on FRIDAY! IAN pages 21-30 due FRIDAY!

  42. Problem Review Activity • Each person will be assigned a color (yellow, orange, or red) • On notebook paper, you will solve the problems only for the color you are assigned • To receive full credit, you must… • 1. Write down your assigned color at the top of your paper • 2. Write down your “givens” (v = 3m/s, etc.) • 3. Show your work to solve the problem • 4. Put a box around your answer • 5. Write all units!

  43. Force, Mass and AccelerationIAN page 32 • Draw the circle AND write the equation for Newton’s second law • Define the variables and the units for each part of the equation • Solve the practice problems

  44. IAN page 33: Momentum • Define momentum • Draw the circle AND write the equation for momentum • Define variables and units for each part of the equation • Solve the three practice problems

More Related