Physics The study of energy & matter and how they interact
Forces a push or pull on an object. Drawn as a vector - have direction and strength Measured in. newtons 5 n
Net Force when in the same direction it is the sum of all forces acting on an object. when in opposite directions it is the difference of the forces Measured in. newtons 5 n 5 n 5n - 5n = 0 n (net force) no movement 5 n 5 n 10 n 5 n Result of all forces on object 5n + 5n = 10 n (net force) movement to right 10n - 5n = 5n (what way will it move?)
Bridge Example Draw & Answer Ms. Dorr puts water in a bucket hanging off your bridge. The bucket is pulled down by gravity with 285 n of force. The reaction force of the bridge is 285 n. What happens to the bridge and why? Ms. Dorr she then adds one cup of water to the bucket increasing the force of gravity on the bucket by 10 n. The reaction force stays the same. What happens to the bridge and why?
Balanced Force Force in one direction the force in the opposite direction Object does not move Net Force = 0 n equals
Unbalanced Force Force in one direction than the force in the opposite direction greater moves in the direction of Object the greater force Net Force > 0n
Newton s 1st Law also called inertia An object at rest will stay at rest and an object in motion will stay in motion (at the same speed & direction) unless an unbalanced force acts on it. objects keep doing what they are doing until acted on by an unbalanced force The greater the mass, the greater the inertia
Newton s 2nd Law Force = mass x acceleration the greater the mass - the greater the force the greater the acceleration (speed) - the greater the force The amount of force something has depends upon its mass and how fast it is going
Newton s 3rd Law For every force there is an equal and opposite force Ex: a book pushes on the table and the table pushes back on it. Action Reaction http://www.teachersdomain.org/resource/phy03.sci.phys.mfw.asrnt/
Friction the force that one surface exerts on another when the 2 rub against each other Always opposite direction of movement movement friction
Energy the ability to do work or cause change to be able to push or pull an object - create force
Potential Energy energy that is stored in an object can be because of its position the higher the object the more the potential energy (gravity) also if you stretch or squish something Example: Yoyo near your hand Rubber band that is stretched rock at the top of a cliff
Kinetic Energy energy of motion The faster the object or the greater the mass, the more kinetic energy potential can be transformed into kinetic Example: Yoyo falling Rubber band released rock falling off cliff
Energy Changes Sometimes kinetic & potential energy can be changed back & forth into eachother. Potential energy can be changed to kinetic Example: Rock falls off cliff Rubber Band is released Kinetic energy can be changed to potential Example: A ball is thrown on the roof pendulum swings up http://www.explorelearning.com/index.cfm?method=cresource.dspview&resourceid=27
Pendulum an object that swings from one point one time that the object swings and then comes back to the same position is called a period http://video.google.com/videosearch?client=safari&rls=en&q=bowling%20ball%20pendulum&ie=utf-8&oe=utf-8&um=1&sa=n&tab=iv
Pendulum Potential Potential 1 2 3 kinetic 4 5 http://www.explorelearning.com/index.cfm?method=cresource.dspview&resourceid=390
Conservation of Energy Energy is not created or destroyed It can be converted from one kind to another Example: Flashlight - electrical energy to light energy Waterwheel - energy of motion to mechanical energy
Galileo On the Moon - acceleration from gravity does not change - is a constant 9.8 m/sec2 http://www.seed.slb.com/en/scictr/lab/galileo/index.htm http://www.teachersdomain.org/ resource/phy03.sci.phys.mfw.galmoon/
Motion change in position or place an object is in motion when its distance from another object changes
Reference Point what you compare an object to when determining if it is in motion.
Speed distance traveled per ONE unit of time Distance/Time Units: miles/hr, meters/sec Example: A student walks 2 miles to school in 0.5 hour what is the speed? 2/0.5 = 4 miles/hour
Constant Speed speed does not change for entire time example: Average Speed speed does change during time calculate by total distance/total time example:
5 4 Distance (m) 3 2 1 0 0 1 2 3 4 5 Time (sec)
Distance vs. Time Graphs RULE The steeper the slope - the greater the speed!!! Slope = Speed
Draw a sketch of a distance-time graph... with two lines, one traveling at a slow speed, one at a faster speed. Label them. fast Distance slow Time
Draw a sketch of a distance-time graph... that is traveling at constant speed distance
Draw a sketch of a distance-time graph... that is not traveling at constant speed distance
Draw a sketch of a distance-time graph... of an object that is standing still distance time
Velocity Distance traveled per unit of time in a specific direction Units: miles/hour in a certain direction Example: 4 miles/hour southwest
Acceleration rate of change in velocity. (speed & direction)
Draw a sketch of a distance-time graph... of an object that is accelerating distance time