Article retrieved from Brittanica, Retrieved 6/27/2016 Velocity Velocity has a scientific meaning that is slightly different from that of speed. Speed is the rate of an object s motion, while velocity designates an object s speed plus the direction of its motion. To calculate an object s speed, one divides the distance it traveled by the amount of time it took: The key difference between speed and velocity is the replacement of distance with displacement: Displacement is the distance traveled in a particular direction, or the object s change in position. Its unit measurement can be meters. To convert a distance into a displacement, one must give a direction. Five meters is a distance. Five meters east describes a displacement. Like displacement, velocity is directional. Velocity is the speed in a particular direction, and it is typically measured in meters per second (m/s or ms 1). Jamie Squire/Getty ImagesJamie Squire/Getty Images The difference between velocity and speed can be illustrated by a person walking around in a circle at a constant speed of 0.5 meters per second. When the person arrives back at the point where he started, he has traveled the distance of the circumference of the circle. His displacement is zero, however, because his position is unchanged. The person s average speed is 0.5 meters per second, but the average velocity is zero. If someone walked from one end of a pier to the other and back, it would be another example of zero displacement of an object. If, on the other hand, the person walked 10 meters to the south on the pier and then stopped, her displacement would be 10 meters south. If it took her 5 minutes to get there, her velocity would be 2 meters per minute south. The velocities described in the above examples are average velocities. The velocity of an object at any moment in time is known as its instantaneous velocity. The instantaneous velocity is the speed in a stated direction at a particular moment in time. Since displacement and velocity have both magnitude (size or strength) and direction, they are called vector quantities. These quantities cannot be specified completely by a number. Another example of a vector quantity isacceleration. Speed, which has magnitude but not direction, is not a vector quantity. Like all vectors, velocity can be represented graphically by an arrow whose length is proportional to its magnitude.
Read It! 1. 2. What makes VELOCITY different from SPEED? Read It! If you walk around 1/4 mile track from the starting line back to the starting line, what is your distance traveled? Read It! 3. 4. If you walk around 1/4 mile track from the starting line back to the starting line, what is your displacement? Read It! What is the difference between instantaneous velocity and average velocity?
Watch It! 1. Go to the following site: melissakennedy.org Click on Weekly Assignments Watch the Brainpop video: Acceleration, under Week of Jan 11th. Watch It! 2. 3. What does speed measure? A. How fast an object is going B. How far an object has traveled C. The rate at which an object slows down D. The rate at which an object speeds up Watch It! Which of the following can be used to measure an object's speed? A. Joules B. Newtons C. Miles per hour D. Kilometers per second per second
Watch It! 4. What does acceleration measure? A. How fast an object is going B. The fastest speed that an object can reach C. The force with which an object travels D. The rate at which speed or direction changes 5. Watch It! Which of these statements is true? A. Acceleration in the direction of motion slows you down B. Acceleration in the direction of motion speeds you up C. Acceleration against the direction of motion has no effect on your speed D. Acceleration against the direction of motion speeds you up 6. Watch It! If you're sitting still in a chair reading this, what is your acceleration? A. 0 m/s/s B. 1 m/s/s C. 2 m/s/s D. 3 m/s/s Watch It! 7. Which of these is an example of acceleration? A. A car coasts along at 40 km/hr B. A car is parked on the side of the road C. A speeding car brakes to a stop D. A car speeds along at 100 km/hr
Explore It! Explore It! 1. Go to the following site: explorelearning.com Log in and complete Activity A on Sled Wars 2. Activity A: Acceleration and speed Get the Gizmo ready: Click Reset. Check that One sled is selected. Set the Red Sled mass to 100 kg. Set the Number of Snowmen to 0. Check that the height of the sled is 50.0 m. Explore It! 3. 4. Speed is the distance moved per unit of time. In this gizmo, units of speed are m/s (meters per second) Question: What factors affect the speed of the sled? Explore It! Observe: With the sled at 50.0 m, click PLAY. Observe the RED SLOPE SPEED SPEEDOMETER. Answer the questions on your answer sheet under Explore It!
Explore It! 5. 6. Experiment: Set the Red sled mass to 10 kg. Click PLAY and then PAUSE after the sled reaches the bottom. Explore It! Explore: Click RESET. Use the Gizmo to measure he sled s final speed when it starts at a height of 10 meters and when it starts at a height of 40 meters. Record these speeds below. 1. Write It! The graph shows a boy mowing the back lawn. The reference point is the dog house. How is the student s speed changing as he mows the lawn?
Write It! 2. 3. How is the student s acceleration changing? Refer to the data on the graph. Write It! What kind of force (balanced or unbalanced) occurs between the student and the lawnmower. How can you tell? Research It! Illustrate It! 1. What is the acceleration of a cheetah? How does a cheetah change its velocity during a hunt? 1. Draw and label a diagram of an item sliding down a hill. Describe how changing the position of the item s starting point affects its acceleration.
Assess It! 1. 2. Dividing the total distance traveled by the total time is how to calculate. A. average speed B. average velocity C. average acceleration D. average motion Assess It! The difference between speed and velocity is that: A. velocity involves time, while speed does not. B. speed involves time, while velocity does not. C. velocity has direction, while speed does not. D. speed has direction, while velocity does not. Assess It! Assess It! 3. In which of the following is a skater NOT accelerating? A. going straight while speeding up B. going straight at constant speed C. making circles at constant speed D. going straight while slowing down 4. Amelia Earhart crossed the ocean in 15 hours at a velocity of 222.6 km/hr East. How far did she travel? A. 3,339 m/s B. 3,330 s C. 3,339 m/s2 D. 3,339 m
Assess It! Assess It! 5. At which line segment is the car NEGATIVELY ACCELERATING? A. OA C. BC B. AB D. CD 6. At which line segment is the car CONSTANT SPEED? A. OA C. BC B. AB D. CD Assess It! Assess It! 7. At which line segment is the car STOPPED? 8. At which line segment is the car moving the FASTEST? A. AB C. CD B. BC D. EF A. AB C. CD B. BC D. EF
Acceleration time Distance velocity speed 426 m/s/s
60 s 24 h 120 min 120 km/h NW 12 km 426 meters
6 m/s/s 12 m/s/s 2 m/s/s 16 mi/h South 83 min 72 m/s
22 cm 612 km 7 m/s/s 1200 m 42 mm 389 cm/s/s
43 milliseconds 22 cm/s Southeast 72 h 1200 m/s East 42 cm/s West 389 cm/s NW
Name: Date: Period: Speed-Velocity-Acceleration Explore it! GIZMO Complete task cards 1-3 on the gizmo, then continue onto task cards 4-6 Task Card 4: Observe with the sled at 50.0 m, click PLAY. Observe the RED sled speedometer. A. What happens to the sled s speed as it moves down the slope? B. Acceleration is a change in speed or direction over time. In what TWO ways does the sled accelerate as it descends? Task Card 6: EXPLORE: Click RESET. Use the Gizmo to measure the sled s final speed when it starts at a height of 10 meters and when it starts at a height of 40 meters. Speed when starting from 10 m: Speed when starting from 40 m: How does increasing the starting height affect the final speed? - Read It! Task Card 1: C. Click RESET. This time focus on the speed of the sled after it reaches the bottom of the hill. Click PLAY. What do you notice? D. Does the sled accelerate after reaching the bottom? Explain. Task Card 5: Click RESET. Sed the RED sled mass to 10 kg. Click PLAY and then PAUSE after the sled reaches the bottom. A. Look at the speedometer. What is the speed of the sled? Task Card 2: Task Card 3: Task Card 4: Watch It! 2. 3. 4. 5. B. Click RESET and change the RED sled mass to 200 kg. Click PLAY. What is the speed of the sled at the bottom now? C. Try other sled masses. Does the mass of the sled affect the final speed? 6. 6. 8.
Task Card 1: Research It! Task Card 1: Illustrate It! Task Card 1: Output Stations Write It! Task Card 2: Task Card 3: Assess It! 1. 2. 3. 4. 5. 6. 7. 8.