Review Video QOD 2/14/12: Compare the scalar of speed and the vector of velocity. What are the equations for each? Feb 14 6:51 AM 1
Imagine that you are a race car driver. You push on the accelerator. The car goes forward, moving faster and faster. As you come up to a curve in the track, you remove your foot from the accelerator to make the turn. In both situations, your velocity changes. When you increase speed, your velocity changes. Your velocity also changes if you decrease speed or if your motion changes direction. Feb 14 6:46 AM 2
acceleration: the rate at which velocity changes over time; an object accelerates if its speed, direction, or both change. practice on page 375 acceleration = final velocity initial velocity time Feb 14 6:49 AM 3
QOD: 2/15/12 1. Calculate the average acceleration of a car that changes speed from 0 m/s to 15 m/s in 5 s. SHOW ALL WORK! 2. Explain why you are always accelerating when you ride a merry go round, even though the speed of the merry go round does not change. (page 373: centripetal acceleration) Feb 14 7:09 AM 4
VELOCITY TIME GRAPHS: Speed Time graphs look much like Distance Time graphs. Be sure to read the labels!! Time is plotted on the X axis. Speed or velocity is plotted on the Y axis. A straight horizontal line on a speedtimegraph means that speed is constant. It is not changing over time. A straight line does not mean that the object is not moving! Feb 14 6:53 AM 5
This graph shows increasing speed. The moving object is accelerating. This graph shows decreasing speed. The moving object is decelerating. Feb 14 6:56 AM 6
Both the dashed and solid line show increasing speed. Both lines reach the same top speed, but the solid one takes longer. The dashed line shows a greater acceleration. Feb 14 6:57 AM 7
A velocity time graph shows us how the speed of a moving object changes with time. The steeper the graph, the greater the acceleration. A horizontal line means the object is moving at a constant speed. A downward sloping line means the object is slowing down. Feb 14 6:58 AM 8
The car is accelerating. The car is slowing down. The car is traveling at a constant speed. The car is stopped. Feb 14 6:59 AM 9
1. Which runner won the race? 4. How long did Bob take to complete the race? 2. Which runner stopped for a rest? 3. How long was the stop? 5. Calculate Albert s average speed. Feb 14 7:03 AM 10
at rest decelerating constant speed accelerating The bus is. Its speed changes from 0 to 10 m/s in 5 seconds. The bus is moving at a of 10m/s for 5 seconds. The bus is. It is slowing down from 10 m/s to rest in 3 seconds. The bus is. It has stopped. The bus is. It is gradually increasing in speed. Feb 14 7:04 AM 11
Table #1 Table #2 On a piece of graph paper, you will be plotting the points for each of these graphs using the graphing strategies discussed today. They should be neat and everything should be properly labeled. When you are finished graphing, you need to calculate the average acceleration (you should have one equation for each table of data). Then, you need to create an original scenario that goes along with each one. Feb 15 7:04 AM 12