Presentation on theme: "color code white – important concepts & information"— Presentation transcript:
1 color code white – important concepts & information aqua – vocabulary termsroyal blue – reminders and supplementary information
2 fundamental forces of nature force of gravitygravity is a force that you feel every daythe electromagnetic forcemost everyday forces, such as friction, are a result of thisthe strong nuclear forcethe weak nuclear forcenuclear forces act only over a short distance
3 forces can act through contact or at a distance fundamental forces vary widely in strength and the distance over which they actforces can act through contact or at a distancepushes and pulls are examples of contact forcesfield forces (like the force of gravity) do not require that the objects touch each otherboth contact and field forces can cause an object to move or to stop moving
4 balanced & unbalanced forces balanced forces do not change motionforces are balanced when the net force is zeronet force - the combination of all forces acting on an objectunbalanced forces do not cancel completelyforces are unbalanced when the net force is greater than zeroobjects accelerate in the direction of the net force
5 frictiona force that opposes motion between two surfaces that are in contactALWAYS opposes the motiontwo typesstatic friction - the force that resists the initiation of sliding motion between two surfaces that are in contact and at restkinetic friction - the force that opposes the movement of two surfaces that are in contact and are moving over each othersstatic friction is ALWAYS greater than kinetic friction
6 not all kinetic friction is the same sliding friction: when objects slide past each otherrolling friction: when a rounded object rolls over a flat surfacein general, rolling friction < sliding friction
7 friction & motion unwanted friction can be lowered using low-friction materials, such as nonstick coatings on cooking pansusing lubricants, such as motor oil, wax, and greasehelpful friction can be increasedscattering sand on icy roads to keep cars from skiddingwearing textured batting gloves when playing baseball to make it easier to grip the bat
8 cars could not move without friction Without friction between the tires and the road, the tires would not be able to push against the road and the car would not move forward.The force pushing the car forward must be greater than the force of friction that opposes the car’s motion.Because of friction, a constant force must be applied to a car just to keep it moving at the same speed.
10 review questionsDescribe three ways to decrease the force of friction between two surfaces that are moving past each other.When you wrap a sandwich in plastic food wrap to protect it, you must first unroll the plastic wrap from the container and then wrap the plastic around the sandwich. In both steps, you encounter friction. In each step, is friction helpful or not? Explain your answer.The force pulling a truck downhill is 2,000 N. What is the amount of static friction acting on the truck if the truck does not move?