1 / 35

Chapter 3

Chapter 3. Forces. Section 1. Newton’s Second Law. Force, Mass and Acceleration. Compare hard thrown ball vs. gently tossed ball Force? Velocity? Acceleration? Throw hard a baseball vs. softball Who goes faster? Why? Velocity and Acceleration depend on __________________.

kamali
Download Presentation

Chapter 3

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. Chapter 3 Forces

  2. Section 1 Newton’s Second Law

  3. Force, Mass and Acceleration • Compare hard thrown ball vs. gently tossed ball • Force? Velocity? Acceleration? • Throw hard a baseball vs. softball • Who goes faster? Why? • Velocity and Acceleration depend on __________________

  4. Newton’s 2nd Law of Motion • Def: _________________________is in the same ________________________ as net force

  5. Net Force • Net Force = mass x acceleration Fnet = ______ • kg x m/s2 = _______________________

  6. Practice! • Rocket has 28,913 N of thrust and a mass of 2,350 kg. What is the acceleration? (frictionless surface) • What is the mass of a rocket that has a thrust of 105 N and an acceleration of 70 m/s2?

  7. Friction • Roll a ball in the parking lot… • Newton’s 1st law says ball will keep ____________________________ • Stops because of friction (negative acceleration – force is __________________) • Def: _________________ that opposes the sliding motion

  8. Microwelds • Def: ____________________where two surfaces come in to contact • Larger force = ________________ microwelds • Break microwelds = ______________ force

  9. Static Friction • Push box = doesn’t move • Acceleration = ______ so net force = _______ • What’s canceling your force? • ___________________: force prevents two surfaces from sliding past each other

  10. Sliding Friction • Def: force that opposes the ________________ motion of two surfaces • Stop pushing = ___________________

  11. Rolling Friction • Car stuck in mud… • Def: ________________________________ between rolling object and surface.

  12. Air Resistance • Falling object pulled by gravity – ___________________by air resistance • Def: _________________ like force opposed motion as moves through __________ • __________________ = objects fall with same acceleration bowling ball vs. feather

  13. Terminal Velocity • Def: ___________________a falling object will reach • When air resistance _________________ downward force • Depends on size, shape, ________________ • Sky diver no parachute vs. with parachute

  14. Section 2 Gravity

  15. What is gravity? • How would you throw a long pass with a football? • Anything that has mass is attracted by gravity • __________________________: attractive force between two objects that depends on masses and ____________________ • Stronger force? • More mass/closer together

  16. Gravity • We only feel ________________ gravitational force • 1 of _______ Basic Forces • Others: • ___________________ force – electricity and magnetism • strong and weak nuclear force – inside nuclei of atoms

  17. Law of Universal Gravitation • Sir Isaac Newton

  18. Earth’s Gravitational Acceleration • When only force acting on two things is gravity – they fall at the _______________rate • Close to earth’s surface acceleration due to gravity is ______________________ • Newton’s second law  _________________ • Fgravity(N) = mass (kg) x acceleration of gravity (m/s2) • F = mg

  19. Weight • Def: ______________________ force on a object • Calculate your weight in N

  20. Weightlessness and Free Fall • When you free fall gravity pulls everything at _____________________ = no gravity • Spaceship in orbit experiences ___________ of earth’s gravity • Ship is in free fall in orbit = no gravity

  21. Projectile Motion • Projectile: anything ______________ or shot through air • Gravity causes path to be _________________ • Horizontal motion – throwing • Vertical motion – ______________

  22. Horizontal and Vertical Distance • Same _____________________ = same mass = same acceleration = same ________________ • Different horizontal distance

  23. Centripetal Force • Centripetal acceleration: acceleration towards the ________________ of a curved path. • Newton’s 2nd law – acceleration in direction of force  __________________________ • Anything moving in circle is because cent. force is accelerating towards center

  24. Gravity

  25. Section 3 Newton’s 3rd Law of Motion

  26. Newton’s 3rd Law • Def: when one object exerts a force on another, the 2nd object exerts an ____________ but ________________ force • Action – __________________ • Jumping on trampoline

  27. Action/Reaction Do NOT Cancel • Forces are equal, but acting on _______________________ objects • Act on water – reaction pushes forward = unbalanced force

  28. Rocket Propulsion • ____________________exerts force on gas backwards – ____________________ exerts force on rocket forwards

  29. Momentum • How much force is needed to change motion? • Def: product of ____________________ and velocity

  30. Practice! • What is the momentum of a 1,300 kg car traveling 28 m/s? • What is the velocity of a 0.15 kg baseball that has a momentum of 6 kg m/s?

  31. Force and Changing Momentum • Catch a foul ball bare handed?

  32. Force and Changing Momentum • F = ma a = (vf – vi) t • Put the two together: • When that baseball hits – calculate the force

  33. Force and Changing Momentum • What is the force of a 0.15 kg baseball with a velocity of 40 m/s when it comes to a stop in 1 second?

  34. Law of Conservation of Momentum • ______________________ doesn’t change unless mass, velocity or both change • Can be _____________________ – pool balls • Def: group of objects exerts forces only on each other, their total momentum doesn’t change

  35. When Objects Collide • 1st puck will give more momentum to the 2nd puck in the same direction • Moving towards each other same speed = ___________ momentum • Collide = 0 momentum – moving same speed ________________ direction

More Related