1 / 10

Force Diagrams

Force Diagrams. And Types of Forces. Review. Force = push or pull. Measured in Newtons. 1 lb = 4.45 N F net = ma a = F net / m Big force = big acceleration Big mass = small acceleration An object’s motion is constant UNLESS a force is applied. Constant velocity = NO NET FORCE!.

salali
Download Presentation

Force Diagrams

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. Force Diagrams And Types of Forces

  2. Review • Force = push or pull. • Measured in Newtons. • 1 lb = 4.45 N • Fnet = ma • a = Fnet / m • Big force = big acceleration • Big mass = small acceleration • An object’s motion is constant UNLESS a force is applied. • Constant velocity = NO NET FORCE!

  3. Types of Forces • Two general classes of force: • Contact forces • Action-at-a-distance forces • Some contact forces • friction, Ff • tension, Ft • normal force, FN • drag (air resistance), Fd • applied force, Fa • spring force, Fs • Some action-at-a-distance forces • gravitational force (weight), Fg or Fw • electric force, FE • magnetic force, FM

  4. Weight • Weight is the force exerted on an object by gravity. • Weight = mass x gravity • Fw = mg • Always oriented downward • On Earth, g = 9.81 m/s2 • Weight changes based on location.

  5. Location g (m/s2) x Earth Weight (N) Weight (lb) 27.1 266 13,300 2980 Sun 0.380 3.73 185 41.6 Mercury 0.907 8.90 445 99.9 Venus 9.81 1.00 491 110. Earth 1.62 0.165 81.4 18.2 Moon 0.377 3.70 185 41.5 Mars 23.3 2.38 1160 261 Jupiter (cloudtops) 1.06 10.4 522 117 Saturn (cloudtops) Pluto 0.651 0.0664 32.8 7.30 Weight of a 50-kg Mass on Selected Bodies

  6. FN FN Fw Fw Normal Force • Normal force – exerted by a surface against an object resting on that surface. • Always perpendicular to surface. • “Normal” means “perpendicular”.

  7. Normal Force • On a horiz. surface, FN = Fw • On a slanted surface, FN = Fw cos = mg cos •  = angle of incline • What is the weight and normal force for a box sitting on a 15º incline if the box’s mass is 150. kg? • Fw = mg • Fw = (150. kg)(9.81 m/s2) • Fw = 1470 N • FN = Fw cos • FN = (1470 N)(cos15º) • FN = 1420 N

  8. Weight vs. Normal Force mg cos FN mg sin mg cos Fw = mg 

  9. Force Diagram • AKA free-body diagram. • Shows all forces acting on an object. • If you can’t draw, don’t worry! • Usu. represent objects as boxes or circles for simplicity. • Forces drawn as vector arrows. • Bigger arrows for bigger forces. • Only draw forces that are known or requested. • Other forces may exist but aren’t important to the problem. • Label force arrows.

  10. Draw a Force Diagram • A box is resting on a horizontal surface. • A box is sliding at constant speed across a horizontal surface. • A box is hanging from a cable. • A box is hanging from two cables that form an angle of 45º. • A box is being pulled along a horizontal plane by a rope that forms an angle of 45º with the floor. • A box is sliding down a frictionless ramp. • A box is sliding down a ramp with friction.

More Related