### Physical Science Powerpoint Presentation

Transcript: Section 3: Motion and force Accident investigators must apply physics formulas to find out the speed and velocity of vehicles involved in an accident. when an object changes position with respect to a frame of reference,the object is in motion Calculating Acceleration Cars could not move without friction Acceleration and Motion Combined velocities determine the resultant velocity v= d/t the force of friction always opposes motion Why is friction sometimes necessary Unbalanced force do not cancel completely The force of friction Acceleration can be seen on a distance vs time graph Friction and Motion friction is necessary for many everyday tasks to work correctly Chapter: 11 Motion Constant: a quantity whose value does not change Frame of Reference- a system for specifying the precise location of objects in space Force: an action exerted on a body in order to change the body's state of rest or motion; force has magnitude and direction Helpful friction can be increased 3. Motion and Force you can plot a graph showing distance on the vertical axis. Graphing Accelerated Motion instantaneous speed is the speed at a given time kinetic friction: the force that opposes the movement of two surfaces that are in contact and are moving over each other What force always opposes motion Friction and motion Speed and velocity speed: the distance traveled divided by time interval during which motion occured. a= whenever there is a net force acting on an object, the object accelerates in the direction of the net force Velocity is described relative to reference point Acceleration can also be a change in direction Accident investigators inspect car accidents or similar events to see who is at fault and determine how much the insurance company should pay. These forces are the force of gravity, the electromagnetic force, the strong nuclear force, and the weak nuclear force Balanced and unbalanced forces Why It Matters Uniform circular motion has centripetal acceleration Balanced forces do not change motion Chapter Outline v/t What do you need to know to find the speed of an object Fundamental forces Calculating speed How can you study speed by using graphs Key ideas What happens when there is a net force acting on an object Fundamental forces vary in strength How do you calculate the acceleration of an object moving in a straight line Static friction: the force that resists the initiation of sliding motion between two surfaces that are in contact and at rest Graphing Motion What changes when an object accelerates Accident investigators can expect to make between $40,000 and $60,000 a year. speed tells us how fast an object moves, and velocity tells us both the speed and direction the object moves Motion can be studied using a distance v. time graph 1. Measuring Motion Acceleration is the rate at which velocity changes Static friction is greater than kinetic friction Why it Matters Graphing Accelerated Motion 4/16/12 The Force of friction Displacement is the change of an object's position Evidence collected from the scene of an accident can be used to learn about the accident. Accident investigators apply physics formulas to find important information, such as the speed of a vehicle at the time the bakes were applied. A good accident investigator combines information from many sources, including skid marks, vehicle damage and witness statements. The investigator must come up with a theory that matches all evidence. Balanced and unbalanced forces How is a frame of reference used to describe motion Acceleration is negative when slowing down. The slope of a distance vs. time graph equals speed To detect motion you must observe the object relative to it's reference points. When you do you can measure distance the object traveled, displacement, speed, and velocity of the object. Acceleration is a change in speed or direction. To calculate acceleration you need the final velocity minus the initial velocity divided by time. A way to graph acceleration is a speed vs. time graph the slope is acceleration. . When forces are applied and produce a net force of zero they are balanced if the net force is above zero they are unbalanced. The force of friction opposes the motion between two surfaces that are in contact. Friction can be increased or lowered by making surfaces rougher or slick. the average acceleration over a given time interval can be calculated by dividing the change in the object's velocity by time over which change occurs Accident Investigator Friction: the force that opposes motion between two surfaces that are in contact Chapter Summary Acceleration and Motion Calculating Speed Acceleration: the rate at which velocity changes over time; an object accelerates if its speed, direction, or both change over time How can a graph be used to find acceleration Acceleration can be a change in speed Speed and Velocity Graphing Motion Observing Motion what do scientist identify as the fundamental forces of nature Unwanted friction can