2Distance vs. Displacement What two changes help you identify that an object is in motion?Change in DirectionChange in Speed
3_______________ is necessary to determine if something is in motion. Frame of Reference: background that appears to be stationary to a moving objectEarth is the most common frame of reference.
4How can something appear to be motionless but actually be moving? If an object has the same frame of reference.If the object is moving at the same speed.Examples?
5Explain how an object can have a zero or negative displacement. Dist. Vs. Disp.DistanceActual path that an object takesCannot be negativeDisplacementStraight line from start to finishCan be negative or zeroThink about your charts made to calculate distance and displacement on the grid.Explain how an object can have a zero or negative displacement.
6Determine the displacement for A and B below. 12 km 6 km
7Calculating Distance and Displacement Pick a starting point on one side of the room, and an ending point on the other side.Have your partner travel to that point.Draw a map on a separate sheet of paper.Using a meter stick, measure the distance traveled and either calculate or measure the displacement. (remember Pythagorean theorem)Show both distance and displacement on your map.
8Speed and Velocity Speed: the rate at which an object changes position Represented by v in a formula.m/s : SI unit for speed
9Instantaneous vs. Average Instantaneous Speed:speed at a particular point in timeEx: Speedometer of a carAverage Speed:speed taken over a distance traveledEx: Calculating your speed over an entire trip
10Speed = distance / time v = d/t What is a good way to represent and describe motion?A distance vs. time graphWhat does the slope of the line in a distance vs. time graph tell you?slope = rise/runspeed = rise (d)/ run (t)
11How is velocity different than speed? Velocity is speed with a direction.Ex: traveling 60 km/hr NorthTwo ways to change velocity:1. Change speed (speed up/slow down)2. Change direction (turn)
12Example ProblemsA car travels 85 km from town A to town B, then 45 km from town B to town C. The total trip took 1.5 hrs. What was the average speed of the car?
13Ex. ContinuedA bicyclist travels for 1.5 hrs at an average speed of 32 km/hr. How far does the bicyclist travel in that time?
14What can you say about the motion of the car in the graph from 8-12 seconds? The car is stopped
15If you were paddling down river at 16 mph and the river moved at 10 mph, how fast would you actually be moving? What if you were paddling up river?
16AccelerationThink of a situation where you were accelerating. What was happening in that situation?Examples:
17Acceleration Acceleration: is the rate of change in velocity Acceleration = change in velocitytimea = vf – viSI unit of acceleration = m/s/s or m/s2
18Free Fall What happens to an object during free fall? The object accelerates at a constant speedAcceleration due to gravity = 9.8 m/s/sFor every second an object falls it will move 9.8 m/s faster
19Ways to Change Acceleration Change SpeedChange DirectionCan you have negative acceleration?yes if the object is slowing down (deceleration)
20v vs. t GraphWhat is the difference between a linear speed vs. time graph and an non linear speed vs. time graph?Linear = constant accelerationNonlinear = changing accelerationSpeedTime
21Example Problems1. A car traveling at 10 m/s starts to decelerate steadily. It comes to a complete stop in 20 s. What is its acceleration?
22Ex. Continued2. An airplane travels down a runway for 4.0s with an acceleration of 9.0 m/s/s. What is its change in velocity during this time?
23Ex. Continued3. A boy throws a rock up into the air. It reaches the highest point of its flight after 2.5 s. How fast was the rock going when it left the boys hand?
244. What is the acceleration from 10 – 20 seconds in the graph below?
25Speed Distance (km) Time (hours) 40 1 100 2 170 3 4 210 5 Graph the following table representing a car trip. Make sure to put the correct labels and units making it a complete graph.What was the average speed for the entire tripWhen was the car traveling at the greatest speed?What happened between the 3rd and 4th hoursGive an example of a dependent variable and explain why it is a dependent variable.Distance (km)Time (hours)4011002170342105
26Which graph shows periods of constant speed? Explain your answer. Graph A shows periods of constant speed (0–8 s, 8–12 s, 12–20 s).
27Describe the motion of the object in Graph A. The object moves at constant speed for 8 seconds, is at rest for the next 4 seconds, and then moves at constant speed for the next 8 seconds.
28Which graph in Figure 11-2 shows acceleration? How do you know? Graph B shows acceleration. The upward slope of the line indicates that an increasing distance is covered each second.
29Using Graph A in Figure 11-2, calculate the average speed of the object in motion from 12 s to 20 s. Explain your calculation.The object moved a distance of 300 m in 8 s. The object’s average speed is 37.5 m/s.
30Compare Graphs A and B in Figure 11-2 Compare Graphs A and B in Figure At a time of 2 seconds, which graph shows a greater velocity? How do you know?Graph A; the slope is steeper.