Chapter 1: Motion Section 1: Describing and Measuring Motion How do you recognize motion?

An object is in motion when its distance from another object is changing An object is in motion when its distance from another object is changing

Chapter 1: Motion Section 1: Describing and Measuring Motion How do you recognize motion? Movement depends on your point of view Movement depends on your point of view Frame of reference Frame of reference

What is a reference point? Frame of Reference A place or object used for comparison to determine if something is in motion A place or object used for comparison to determine if something is in motion An object is in motion if it changes position relative to a reference point An object is in motion if it changes position relative to a reference point

What is the basic unit of length? The meter – a little longer than a yard The meter – a little longer than a yard

What do scientists use to measure the length of an object smaller than a yard? A centimeter – one hundredth of a meter, so there are 100 centimeters in a meter A centimeter – one hundredth of a meter, so there are 100 centimeters in a meter A millimeter – There are 1,000 millimeters in a meter A millimeter – There are 1,000 millimeters in a meter

How do scientists measure long distances? The kilometer – There are 1,000 meters in 1 kilometer The kilometer – There are 1,000 meters in 1 kilometer

How do scientists calculate speed? Speed – the distance the object travels in one unit of time Speed – the distance the object travels in one unit of time Rate – tells you the amount of something that occurs or changes in one unit of time Rate – tells you the amount of something that occurs or changes in one unit of time Speed = distance Speed = distance time time

What is constant speed? If the speed of an object does not change, the object is traveling at a constant speed If the speed of an object does not change, the object is traveling at a constant speed

What is average speed? Most objects do not move at constant speeds for very long Most objects do not move at constant speeds for very long To find average speed divide the total distance by the total time To find average speed divide the total distance by the total time Car trip

What is Velocity? Speed in a given direction Speed in a given direction When you know the speed and direction of an object’s motion, you know the velocity of the object When you know the speed and direction of an object’s motion, you know the velocity of the object Example: 15 km/hour westward Example: 15 km/hour westward

How do you graph motion? You can show the motion of an object on a line graph in which you plot distance against time You can show the motion of an object on a line graph in which you plot distance against time Time is along the x- axis and distance on the y-axis Time is along the x- axis and distance on the y-axis

How do you interpret motion graphs? A straight line indicates a constant speed A straight line indicates a constant speed The steepness depends on how quickly or slowly the object is moving The steepness depends on how quickly or slowly the object is moving The faster the motion the steeper the slope The faster the motion the steeper the slope

Section 2: Slow motion on Planet Earth According to their explanation, known as the theory of plate tectonics, Earth’s plates move ever so slowly in various directions According to their explanation, known as the theory of plate tectonics, Earth’s plates move ever so slowly in various directions

How fast do plates move? Some small plates can move as much as several centimeters per year, whereas other move only a few millimeters per year Some small plates can move as much as several centimeters per year, whereas other move only a few millimeters per year

How can you calculate the distance an object has moved? Rearrange the speed formula Distance = Speed x Time Converting units – choose a conversion factor that will allow you to cancel units D S T

Section 3: Acceleration What is Acceleration? The rate at which velocity changes The rate at which velocity changes In science, acceleration refers to: In science, acceleration refers to: increasing speed increasing speed decreasing speed decreasing speed changing direction changing direction

Acceleration Whenever an objects speed increases, the object accelerates. Whenever an objects speed increases, the object accelerates. Pitcher throwing a softball Pitcher throwing a softball Car moving from a stopped position Car moving from a stopped position

Acceleration Whenever an objects speed SLOWS DOWN, the object decelerates or has negative acceleration. Whenever an objects speed SLOWS DOWN, the object decelerates or has negative acceleration. Softball landing in the catcher’s glove. Softball landing in the catcher’s glove. Car stopping at a red light. Car stopping at a red light.

Acceleration Acceleration can be a change in direction as well as a change in speed. Acceleration can be a change in direction as well as a change in speed. Runners accelerate as the round a curve Runners accelerate as the round a curve car accelerates as it follows a curve in the road car accelerates as it follows a curve in the road a softball accelerates as it is hit by a bat. a softball accelerates as it is hit by a bat.

Acceleration Many objects continuously change direction without changing speed. Many objects continuously change direction without changing speed. Circular motion – a motion along a circular path. Circular motion – a motion along a circular path. Ex. Seats on a Ferris wheel Ex. Seats on a Ferris wheel

Stop and Think How can a car be accelerating if its speed is constant at 65 km/hr? How can a car be accelerating if its speed is constant at 65 km/hr?

How do you calculate acceleration? To determine the acceleration rate of an object, you must calculate the change in velocity during each unit of time To determine the acceleration rate of an object, you must calculate the change in velocity during each unit of time Acceleration = Final velocity – Initial velocity Acceleration = Final velocity – Initial velocity Time Time

How do you interpret graphs to determine acceleration? The acceleration at any moment is equal to the slope of the velocity time graph at that moment in time The acceleration at any moment is equal to the slope of the velocity time graph at that moment in time Acceleration vs. Constant speed