2 Reference pointa place or object used for comparison to determine if something is in motion.
3 Suppose 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?
4 Motionan 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).
5 Speed 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
6 Sample Problem:At what speed did a plane fly if it traveled 1760 meters in 8 seconds?
7 Practice 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?
8 Velocity speed in a given direction. Velocity = Distance Time Note that the velocity equation is the same as the speed equation
9 Graphing 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
10 Accelerationthe 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
11 Practice 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?
12 Graphing Acceleration Velocity vs. TimeVelocity on y-axisTime on x-axisThe slope of the line gives you the acceleration of the object.
13 Final 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