2What is Motion? Section 1an 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).
3Reference pointa place or object used for comparison to determine if something is in motion.
4Suppose 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?
5Distance and Displacement Distance – the total length of the route you will travel.Odometers measure distance traveled.It is 4 miles to drive from my house to school.Displacement – the distance between the starting and ending points and the direction in which you traveled.“As the crow flies.”It is 1.3 miles from my house to school as the crow flies. A straight line distance.
6Speed The distance an object travels in one unit of time is it’s speed.Speed = DistanceTimeUnits of Speed = (m/s) or (km/hr)Average speed = total distancetotal time
7The 3-Step Process FOR SHOWING MATH WORK IN SCIENCE Step 1: Formula Step 2: Substitute (with units)Step 3: Solve (with units!!)Ex:F=maF=20kg x 0.5m/s/sF=10kgxm/s/s = 10N
8Sample Problem:At what speed did a plane fly if it traveled 1760 meters in 8 seconds?
9Step 1: Formula v = d/t Step 2: Substitute v = 1760m / 8s At what speed did a plane fly if it traveled 1760 meters in 8 seconds?Step 1: Formulav = d/tStep 2: Substitutev = 1760m / 8sStep 3: Solvev = 220 m/s
10Speed 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?
11Average vs Instantaneous Speed Average speedSpeed can change during the time traveled.Speeding up and slowing downStopping at traffic lightsGetting behind slower driversStopping to use the rest-room or to get a drink at the convenient storePassing the semi-truck in front of youTraffic jamAverage speed is TOTAL distance traveled during the TOTAL time traveled!!
12Instantaneous Speed The speed of an object at one instant of time Right NOW!Shown on the speedometer!
13Velocity speed in a given direction. Velocity = Distance Time Note that the velocity equation is the same as the speed equationA change in v happens when:1 it’s speed changes2 it’s direction changes3 they both change
14Graphing 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
15Acceleration Section 2 the rate of change in velocity. Refers to:increasing speed (speeding up) – positive acceldecreasing speed (slowing down) – negative accelor changing direction (turn)(a)=Final Velocity (vf)-Initial Velocity (vi) Time (t)a = vf – vitUnits for Acceleration: km/hr2, km/hr/s or m/s2
16Acceleration 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?
17Graphing Acceleration Velocity vs. TimeVelocity on y-axisTime on x-axisThe slope of the line gives you the acceleration of the object.
18Momentum Section 3When a collision occurs, changes in motion of the colliding objects depend on their masses and their velocities before the collision.
19Mass and InertiaWould it be harder to stop a large adult from rushing at you or a small child?Why?Inertia is a property of matter which states that objects have the tendency to resist a change in its motion!Objects with more mass have more inertia!
20Momentum This is a measure of how hard it is to stop an object. Momentum (p) = mass (m) x velocity (v)p=mvMass is measured in kgVelocity is measured in m/sUnits of momentum are kg*m/s
21Momentum Practice Problems Calculate the momentum of a 14kg bicycle traveling north at 2.0m/sA 10,000kg train is traveling east at 15m/s. What is the momentum of the train?What is the momentum of a car with a mass of 900kg traveling north at 27m/s?
22Final 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