Movement depends on your point of view 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 Movement depends on your point of view
What is a reference point? 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
What is the basic unit of length? The meter – a little longer than a yard
A millimeter – There are 1,000 millimeters in a meter 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 millimeter – There are 1,000 millimeters in a meter
How do scientists measure long distances? The kilometer – There are 1,000 meters in a kilometer
How do scientists calculate speed? 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 Speed = distance time
What is 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 To find average speed divide the total distance by the total time Car trip
What is Velocity? Speed in a given direction When you know the speed and direction of an object’s motion, you know the velocity of the object 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 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 The steepness depends on how quickly or slowly the object is moving 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
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
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
Section 3: Acceleration What is Acceleration? The rate at which velocity changes In science, acceleration refers to: increasing speed decreasing speed changing direction
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 Acceleration = Final velocity – Initial velocity Time
How do you interpret graphs to determine acceleration? Acceleration vs. Constant speed The acceleration at any moment is equal to the slope of the velocity time graph at that moment in time
v d t