2Reference pointa place or object used for comparison to determine if something is in motion.
3Suppose you are standing on a sidewalk and your friend rides past you on her skateboard. Which one of you is moving relative to the Earth?Are you moving relative to your friend?
4Motionan object is in motion if it changes position relative to a reference point.An object moves when its distance from another object is changing.Whether an object is moving or not depends on your point of view (reference point).
5Speed The distance an object travels in one unit of time is it’s speed.Speed = DistanceTimeUnits of Speed = (m/sec) or (km/hr)Average speed = total distancetotal time
6Sample Problem:At what speed did a plane fly if it traveled 1760 meters in 8 seconds?
7Practice Problems:A car travels 240 kilometers in 3 hours. What is the speed of the car during that time?The speed of a cruise ship is 50 km/hr. How far will the ship travel in 14 hours?A cyclist travels 32 km during the first 2 hours of riding, and 13 km during the next hour. What is the average speed of the cyclist?
8Velocity speed in a given direction. Velocity = Distance Time Note that the velocity equation is the same as the speed equation
9Graphing motionAlways use a distance vs. time graph (distance on the vertical or y-axis and time on the horizontal or x-axis).Slope – tells you the rate of change (speed).slope = riserun
10Accelerationthe rate of change in velocity. Refers to increasing speed, decreasing speed, or changing direction.(a)=Final Velocity (fv)-Initial Velocity (iv) Time (t)a = fv – ivtUnits for Acceleration: km/hr2, km/hr/s or m/sec2
11Practice Problems:A roller coaster is moving at 25m/sec at the bottom of a hill. Three seconds later it reaches the top of the next hill, moving at 10m/sec. What is the deceleration of the roller coaster?A car is traveling at 60km/hr. It accelerates to 85km/hr in 5 seconds. What is the acceleration of the car?
12Graphing Acceleration Velocity vs. TimeVelocity on y-axisTime on x-axisThe slope of the line gives you the acceleration of the object.
13Final Practice Problems One jet plane is flying east at 880 km/h, and another plane is traveling north at 880 km/h. Do they have the same velocities? The same speeds? Explain.A swimmer speeds up from 1.1 m/s to 1.3 m/s during the last 20 seconds of the workout. What is the acceleration during this interval?Describe three different ways to change your velocity when you’re riding a bicycle.An object is said to be accelerating if it ___________.a) speeds up c) changes directionb) slows down d) all of these