EQ: How can you describe an object’s motion?

EQ: How can you describe an object’s motion? EXPLORE

Basic INFO Description: In this activity, you will be investigating the relationships between speed, velocity and acceleration Materials: 1 Explore Student Guide: Motion (per person) 1 sharpie 1 ruler 1 timing device 4 Ziploc baggies 400 ml sand 1 8th grade science book masking tape Time: 3 days

Instructions --- Day 1 Follow along with me as I read the background information you will need as you explore the concepts of speed, distance, velocity and acceleration Re-read the background information to yourself Answer the background questions in your student journal. Discuss your answers with your group mates and come to a consensus as to how each question should be answered. Move on to Part I: Plan your investigation: Your mission is to develop an investigation to compare the speed, velocity, and acceleration of a person as s/he completes different walks You will collect distance and time data for a person on several different short walks. Then you will calculate the speed and velocity of the walker during different intervals of the walk. Inquiry Question: How does the motion of an object relate to its speed, velocity and acceleration? Materials you may use: 1 sharpie, 1 ruler, 1 timing device,4 Ziploc baggies, 400 ml sand, 1 8th grade science book , masking tape Finally, you will create distance vs. time graphs and speed vs. time graphs to represent the motion during each walk Complete Part I : Plan your investigation and gather materials needed for tomorrow

Instructions --- Day 2 Finish Part I: Plan Your Investigation Gather your materials Put them in the box in the center of the table Find an area in which to collect data See Mrs. Belaski for area assignment Collect the data for 4 walks Change speed and/or velocity for each one Record the data (Part II: Implement Your Investigation) Graph and analyze your data See Mrs. Belaski for guidance!

Instructions --- Day 3 Finish collecting data Graph the collected data Distance vs. Time Distance --- meters Time ---seconds Determine scale as a group Speed vs. Time Must find rate of speed first Speed=Distance/Time Speed --- meters/second Time --- seconds Answer Reflections and Conclusions as a group

EQ: How can an object’s motion be described? Explain: Motion

Motion Motion is the process of moving an object from one place to another. An object’s motion can be described by its: Speed Velocity Acceleration Momentum

Speed A measurement of distance can tell you how far an object travels. A cyclist, for example, might travel 30 kilometers. An ant might travel 2 centimeters. If you know the distance an object travels in a certain amount of time, you can calculate the speed of the object.

Speed Speed is a type of rate. A rate tells you the amount of something that occurs or changes in one unit of time. The speed of an object is the distance the object travels in a certain amount of time

Speed To calculate the speed of an object, divide the distance the object travels by the amount of time it takes to travel that distance. This relationship can be written as an equation: Speed = Distance/Time

Speed Speed is expressed in terms of the distance traveled followed by the amount of time taken to travel Kilometers/hr Miles/hr Meters/second

Average Speed The speed of most moving objects is not constant. Average speed is: the total distance traveled divided by the total time elapsed. To calculate average speed, divide the total distance traveled by the total time. Average Speed= Distance Traveled/Total Time

Instantaneous Speed Calculating the average speed of an object is important. However, it is also useful to know an object’s instantaneous speed. Instantaneous speed is the rate at which an object is moving at a given instant in time.

Velocity Knowing the speed at which something travels does not tell you everything about its motion. To describe an object’s motion completely, you need to know the direction of its motion

Velocity For example, suppose you hear that a thunderstorm is traveling at a speed of 25 km/h. Should you prepare for the storm? That depends on the direction of the storm’s motion. Because storms usually travel from west to east in the United States, you need not worry if you live to the west of the storm. But if you live to the east of the storm, take cover.

Velocity When you know both the speed and direction of an object’s motion, you know the velocity of the object. Speed in a given direction is called velocity. EX: northward, southward, etc. Velocity = distance/time + the direction of motion You know the velocity of the storm when you know that it is moving 25 km/h, eastward.

Graphing Velocity

Graphing Velocity Velocity is graphed with the time traveled across the bottom (x –axis) and the speed along the side (y-axis) V= distance/time + the direction of motion This graph shows a constant velocity as the object is moving at a rate of 10 m/s in the same direction throughout the graph

Constant Velocity This graph also shows constant velocity, as this object is moving at a constant rate of 5 m/s in the same direction throughout the journey.

Changing Velocity While this object is traveling in the same direction throughout, it does not have the same speed through out. It accelerates both positively and negatively Therefore, it does not have a constant velocity

Changing Velocity This graph shows a change in direction, as the line crosses the x-axis It does not have a constant velocity

Acceleration Most examples of motion involve changes. In fact, rarely does any object’s motion stay the same for very long.

Acceleration Suppose you are a passenger in a car stopped at a red light. When the light changes to green, the driver steps on the accelerator. As a result, the car speeds up, or accelerates. In everyday language, acceleration means “the process of speeding up.”

Acceleration Acceleration has a more precise definition in science. Velocity is a rate, and scientists define acceleration as the rate at which velocity changes. Recall that velocity describes both the speed and direction of an object. A change in velocity can involve a change in either speed or direction—or both. Acceleration = Final Speed – Initial Speed/Time In science, acceleration refers to increasing speed, decreasing speed, starting , stopping or changing direction.

Acceleration Initial speed= 4 m/s Final speed = 22 m/s Time = Acceleration = Final speed – initial speed/time Initial speed= 4 m/s Final speed = 22 m/s Time = 3 seconds Acceleration = 22m/s-4m/s / 3s Acceleration = 18 m/s / 3 s Acceleration = 6 m/s2 The rollercoaster’s average acceleration is 6 m/s 2 As a rollercoaster starts down a slope, it’s speed is 4m/s. 3 seconds later, at the bottom, it’s speed is 22 m/s What is its average acceleration?

Momentum Momentum is defined as the quantity of motion of a body. According to Newton, momentum causes an object in motion to remain in motion unless it’s acted on by some other force. So the momentum of a moving object is related to its mass and its velocity. Because momentum is related to mass and velocity, it takes a lot of force to stop the momentum of a heavy object that’s traveling at high speed. Momentum measures how hard it will be to stop the object.

Momentum An object with a large mass or a fast velocity has a large amount of momentum. The more momentum an object has, the harder it is to stop. A speeding truck has a large amount of momentum. A mouse does not Momentum = mass x velocity Calculate the momentum when a 10-kg object move with a speed of 5 m/s 10 kgX5 m/s= 50 kg m/s