Motion, Forces and Energy Chapter 1
Chapter 1: Motion Section 1: Describing and Measuring Motion When is an object in motion? How do you know an object’s speed and velocity? How can you graph motion?
Section 1: Describing and Measuring Motion Observing Motion: Motion: distance from another object changes Reference Point An object that appears to be in place or an object used for comparison to detect motion Object in motion if it changes position relative (compared to ) the reference point Relative Motion Motion dependent on reference point Example: sky divers
Observing Motion Common Reference Point Nonmoving objects such as buildings, trees, and mountains Moving objects could also serve as reference point; bird flying by hot air balloon Earth is a moving reference point; moving around the Sun
Section 1: Describing and Measuring Motion Measuring Distance International System (SI) : system of measurement used around the world Meter: SI unit of length
Speed Depends on Distance and Time Speed—the rate at which an object moves Depends on distance travelled and time taken to travel distance SI unit—meters per second m/s The Speed Equation Speed = Distance/Time Example: 30m/5s = 6m/s
Section 1: Calculating Speed Average Speed Average Speed = Total Distance/Total Time Rate is not constant Instantaneous Speed Rate an object is moving at a specific time (at that instant)
Section 1: Describing Velocity Velocity: speed in a certain direction Example 25 mph East
Velocity: Direction Matters Velocity Changes as Speed or Direction Changes Velocity constant only if speed and direction do not change Velocity changes if speed or direction changes
Velocity: Direction Matters Combining Velocities Resultant Velocity Combine the velocities if the velocities are in the same direction Subtract the smaller velocity from the large velocity if traveling in opposite directions
Section 1: Graphing Motion Graph Motion on a Line Graph X-axis: Time Y-axis: Distance The slope (curve of the line) is the speed Steeper the slope the faster the speed Slope = Rise/Run
Section 2: Slow Motion on the Planet Earth How does the theory of plate tectonics explain the movement of Earth’s landmasses? How fast do Earth’s plates move?
Earth’s Plates Plates: Pieces of earth’s crust broken into these pieces Theory of Plate Tectonics Earth’s plates move slowly in various directions; this has caused the movement of continents Why Do Earth’s Plates Move? Currents within the mantle are caused by rising hot molten rock and sinking cooler rock New material at fault lines also cause movement
Plate Movement Plates move very slowly Centimeters per year
Section 3: Acceleration What kind of motion does acceleration refer to? How is acceleration calculated?
What is Acceleration? Acceleration: rate of the chance in velocity Could: Speed UP Could Slow Down Could be a change in DIRECTION
What is Acceleration? Calculating Acceleration Acceleration = final speed – initial speed / Time SUBTRACT initial (starting)speed from the final (ending) speed and DIVIDE by the time Example: Initial speed 0m/s; Final speed 10m/s; Time 5 seconds 10-0 / 5 = 2m/s2
Acceleration: The Rate at Which Velocity Changes Defining ACCELERATION Acceleration: THE RATE AT WHICH VELOCITY CHANGES Acceleration changes SPEED or TIME changes Acceleration is also DIRECTIONAL changes
Acceleration: The Rate at Which Velocity Changes Calculating Acceleration Acceleration = final velocity – starting velocity time it takes to change velocity Acceleration expresses as m/s2
Acceleration: The Rate at Which Velocity Changes Examples of Acceleration Positive acceleration: velocity INCREASES Negative acceleration (deceleration): velocity DECREASES Acceleration would also change if direction changes
Acceleration: The Rate at Which Velocity Changes Circular Motion: Continuous Acceleration CENTRIFUGAL acceleration: acceleration that occurs in circular motion Objects travelling in circular motion are always CHANGING velocity