2 Force a push or pull acting on an object typically measured in Newtons (kg•m/s2)is a vectorcan be combined to predict motion net forceSoccer Simulation
3 Types of Forces Contact Forces Non-Contact Forces Applied Normal FrictionAir ResistanceTensionSpringNon-Contact ForcesGravityElectromagnetic
4 Applied Forceany push or pull on an object created from another source (person, animal, another object, etc.)
5 Normal Forcethe support force exerted on an object directly related to weight (gravity)consequence of Newton’s 3rd Lawis always perpendicular to the surfaces in contactGravity900Gravity900BoxBoxFrictionNormalForceNormalForce
6 is the force (friction) exerted by a surface as an object moves across it or attempts to move across itopposes the motion of an objectdepends on the type of surfaces and the normal force (weight)TypesKineticStaticIn which directionis the force (friction)vector pointing?MotionFriction
7 Air Resistance friction due to air molecules acts upon objects as they travel through the airopposes the motion of an objectmost noticeable for objects traveling at fast speedsExamplesSpace shuttle re-entryMeteorite in FreeholdMeteor over Russia
8 Minimizing Air Resistance (Drafting) used in variety of competitive events (bicycle and car racing, swimming, etc.) to reduce air resistanceNotice how the second biker experiences less air resistance because he is shielded by the first biker.Image taken from:Although it does not workexactly the same way, whereis these seen in nature?
9 Tensionforce that is transmitted through a string, rope, cable or wire when it is PULLED tight by forces acting from opposite endsdirected along the length of the wire and PULLS equally on the objects on the opposite ends of the wire
10 Springforce exerted by a compressed or stretched spring upon any object that is attached to itfor most springs, the magnitude of the force is directly proportional to the amount of stretch or compression of the springImages taken from:If both springs are the same size when not compressed, which spring will apply more force to the ball when released? Explain your reasoning.
11 Gravity natural force of attraction between any two objects factors: distance – increased distance less gravitational pull or vice versamass – increased mass more gravitational pull or vice versaWhy does the force of gravity have more of an impact on holding our solar system together compared to holding the parts of an atom together?
12 Electromagnetic Force force that moving charges exert on one anotherresults from the repulsion of like charges and the attraction of oppositesNotice how the particles with the same charge move apart and the particles with different charges move together.+++---Compare and contrast gravitational force and electromagnetic force.
13 Free Body Diagrams visuals that help show net force Practice use a square and draw all forces acting on the object.remember size and direction of vector arrows are important!PracticeFgrav = 5 NFfric = 3 NFnorm = 5 NFapp = 3 NWhat do you think thesymbols w/subscriptsrepresent?What is the netforce on this object?
14 You throw a baseball to your friend who is to your left. What’s the Net ForceFnorm = 10 NFapp = 20 NFfric = 5 NFfric = 5 NFapp = 15 NFgrav = 10 NFgrav = 10 NYou throw a baseball to your friend who is to your left.Your dog pulls you down the street on a skateboard in an eastward direction.
15 What’s the Net Force (An Interesting Case) A skydiver is descending with a constant velocity. Consider air resistance.The same skydiver is descending after 30 seconds. Consider air resistance.FgravFfricFgravFfricWhat has the skydiver reached in this scenario?
16 LawsNewton’s 1st LawNewton’s 2nd LawNewton’s 3rd Law
17 Newton’s 1st Lawobjects at rest remain at rest, and objects in motion remain in motion with the same velocity, unless acted upon by an unbalanced forcealso considered the Law of InertiaHow is this illustrated when riding in a car? Can you think of otherexperiences where this is illustrated?
18 Inertiathe resistance of an object to a change in the speed or the direction of its motiondirectly related to mass
19 Newton’s 2nd Lawthe acceleration of an object increases with increased force and decreases with increased massthe direction in which an object accelerates is the same as the direction of the forceFormula: F = ma (or a = F/m)Shopping Cart Simulation
20 In this case, the force of the Centripetal Forceany force that keeps an object moving in a circledirected toward the center of the circleIn this case, the force of theball as it accelerates around the circle is pointing inward, toward the center.
21 Practice Problems - Force What net force is needed to accelerate a 24 kg dogsled to a rate of 3 m/s2?2. A 1.5 kg object accelerates across a smooth table at a rate of 0.5 m/s2? What is the unbalanced force applied to it?72 kg·m/s2or 72 NF = maF =(24 kg)(3 m/s2)=F =(1.5 kg)(0.5 m/s2)F = ma=0.75 kg·m/s2or 0.75 N
22 Newton’s 3rd Lawstates that every time one object exerts a force on another object, the second object exerts a force that is equal in size and opposite in direction back on the first object.How was this illustrated during the Scooter Games competition? Can you think of other experiences where this is illustrated?
23 Vector a quantity that has both direction and magnitude (size) drawn as an arrow which shows direction and magnitude (length of arrow)consists of two parts: tail and headHeadTailConsider the vectors above. Describe the direction and relative magnitude (force) of each ball based on the vector.
24 What is the hockey puck’s net force? Combining Vectorscan be combined/added to help determine net forcethe overall force acting on an object when all of the forces acting on it are combinedWhat is the hockey puck’s net force?Gravity = 14 NNormal Force = 14 NGravity = 14 NApplied Force = 25 NFriction = 2 N23 NApplied Force = 25 NFriction = 2 NNormal Force = 14 N