Chapter 10 Section 1 Measuring Motion Objectives Explain the relationship between motion and a frame of reference. Relate speed to distance and time. Distinguish between speed and velocity. Solve problems related to time, distance, displace-ment, speed, and velocity.

Chapter 10 Observing Motion Section 1 Measuring Motion Observing Motion Motion is an object’s change in position relative to a reference point. Displacement is the change in the position of an object. Distance measures the path taken. Displacement is the change of an object’s position. Displacement must always indicate direction.

Chapter 10 Section 1 Measuring Motion Motion

Distance vs. Displacement Chapter 10 Section 1 Measuring Motion Distance vs. Displacement Teaching Transparency

Chapter 10 Speed and Velocity Section 1 Measuring Motion Speed and Velocity Speed is the distance traveled divided by the time interval during which the motion occurred. Speed describes how fast an object moves. Speed measurements involve distance and time. The SI units for speed are meters per second (m/s). When an object covers equal distances in equal amounts of time, it is moving at a constant speed.

Chapter 10 Section 1 Measuring Motion Speed

Speed and Velocity, continued Chapter 10 Section 1 Measuring Motion Speed and Velocity, continued Speed can be studied with graphs and equations. Speed can be determined from a distance-time graph. When an object’s motion is graphed by plotting distance on the y-axis and time on the x-axis, the slope of the graph is speed.

Speed and Velocity, continued Chapter 10 Section 1 Measuring Motion Speed and Velocity, continued Average speed is calculated as distance divided by time. Equation for Average Speed Instantaneous speed is the speed at a given point in time.

Chapter 10 Section 1 Measuring Motion Math Skills Velocity Metal stakes are sometimes placed in glaciers to help measure a glacier’s movement. For several days in 1936, Alaska’s Black Rapids glacier surged as swiftly as 89 meters per day down the valley. Find the glacier’s velocity in m/s. Remember to include direction. List the given and the unknown values. Given: time, t = 1 day displacement, d = 89 m down the valley Unknown: velocity, v = ? (m/s and direction)

Chapter 10 Math Skills, continued Section 1 Measuring Motion Math Skills, continued 2. Perform any necessary conversions. To find the velocity in meters per second, the value for time must be in seconds.

Chapter 10 Math Skills, continued 3. Write the equation for speed. Section 1 Measuring Motion Math Skills, continued 3. Write the equation for speed. 4. Insert the known values into the equation, and solve.

Speed and Velocity, continued Chapter 10 Section 1 Measuring Motion Speed and Velocity, continued Velocity is the speed of an object in a particular direction. Velocity describes both the speed and the direction. Combine velocities to determine the resultant velocity.

Speed and Velocity, continued Chapter 10 Section 1 Measuring Motion Speed and Velocity, continued

Chapter 10 Velocity Section 1 Measuring Motion Click below to watch the Visual Concept. Visual Concept

Chapter 10 Section 2 Acceleration Objectives Describe the concept of acceleration as a change in velocity. Explain why circular motion is continuous acceleration even when the speed does not change. Calculate acceleration as the rate at which velocity changes. Graph acceleration on a velocity-time graph.

Acceleration and Motion Chapter 10 Section 2 Acceleration Acceleration and Motion Acceleration is the rate at which velocity changes over time. An object accelerates if its speed, direction, or both change.

Chapter 10 Section 2 Acceleration Acceleration

Acceleration and Motion, continued Chapter 10 Section 2 Acceleration Acceleration and Motion, continued Acceleration can be a change in speed. Acceleration can be a change in direction. Uniform circular motion is constant acceleration.

Centripetal Acceleration Chapter 10 Section 2 Acceleration Centripetal Acceleration

Calculating Acceleration Chapter 10 Section 2 Acceleration Calculating Acceleration Acceleration is the rate at which velocity changes. Acceleration Equation (for straight-line motion) In SI units, acceleration is measured in meters per second per second (m/s/s) or m/s2.

Chapter 10 Section 2 Acceleration Math Skills Acceleration A flowerpot falls off a second-story windowsill. The flowerpot starts from rest and hits the sidewalk 1.5 s later with a velocity of 14.7 m/s. Find the average acceleration of the flowerpot. 1. List the given and the unknown values. Given: time, t = 1.5 s initial velocity, vi = 0 m/s final velocity, vf = 14.7 m/s down Unknown: acceleration, a = ? (m/s2 and direction)

Chapter 10 Math Skills, continued Section 2 Acceleration Math Skills, continued 2. Write the equation for acceleration. 3. Insert the known values into the equation, and solve.

Calculating Acceleration, continued Chapter 10 Section 2 Acceleration Calculating Acceleration, continued Acceleration can be determined from a velocity-time graph.

Graphical Representations of Acceleration Chapter 10 Section 2 Acceleration Graphical Representations of Acceleration

Chapter 10 Section 3 Motion and Force Objectives Explain the effects of unbalanced forces on the motion of objects. Compare and contrast static and kinetic friction. Describe how friction may be either harmful or helpful. Identify ways in which friction can be reduced or increased.

Chapter 10 Bellringer Section 3 Motion and Force The concept of force explains many occurrences in our everyday lives. From your own experience, state what will happen in the following situations: A marble is placed at the top of a smooth ramp. What happens to the marble? What force causes this? A marble is rolling around in the back of a small toy wagon as the wagon is pulled along the sidewalk. When the wagon is stopped suddenly by a rock under one of the wheels, the marble rolls towards the front of the wagon. Why does the marble keep going when the wagon stops? (Hint: Consider what it takes to change the velocity of the wagon and the marble.) If you dropped a flat uncrumpled sheet of notebook paper and a similar piece of notebook paper that was crushed into a ball from the same height, which would reach the floor first? Why are the forces on these two pieces of paper different?

Balanced and Unbalanced Forces Chapter 10 Section 3 Motion and Force Balanced and Unbalanced Forces Force is an action exerted on a body in order to change the body’s state of rest or motion. Force has magnitude and direction. The net force is the combination of all forces acting on an object. Objects subjected to balanced forces either do not move or move at constant velocity. An unbalanced force must be present to cause any change in an object’s state of motion or rest.

Chapter 10 Section 3 Motion and Force Force

Chapter 10 The Force of Friction Section 3 Motion and Force The Force of Friction Friction is a force that opposes motion between two surfaces that are in contact. Friction opposes the applied force.

The Force of Friction, continued Chapter 10 Section 3 Motion and Force The Force of Friction, continued

The Force of Friction, continued Chapter 10 Section 3 Motion and Force The Force of Friction, continued Static friction resists the initiation of sliding motion between two surfaces that are in contact and at rest. Kinetic friction opposes the movement of two surfaces that are in contact and are sliding over each other. Static friction is greater than kinetic friction. There are many different types of kinetic friction, such as sliding friction and rolling friction. Fluid friction, such as air resistance, also opposes motion.

Chapter 10 Section 3 Motion and Force Types of Friction

Frictional Forces and Acceleration Chapter 10 Section 3 Motion and Force Frictional Forces and Acceleration

Chapter 10 Friction and Motion Friction can be helpful or harmful. Section 3 Motion and Force Friction and Motion Friction can be helpful or harmful. Friction is necessary to roll a vehicle or hold an object. However, friction can also cause excessive heating or wear of moving parts. Harmful friction can be reduced. Helpful friction can be increased.

Ways to Reduce or Increase Friction Chapter 10 Section 3 Motion and Force Ways to Reduce or Increase Friction

Understanding Concepts Chapter 10 Standardized Test Prep Understanding Concepts 1. A bicyclist traveling at 10 m/s applies her brakes, reducing her velocity to 5 m/s. If it takes 2 seconds to slow the bike, what is the acceleration during that period? A. –5 m/s2 B. –2.5 m/s2 C. 0 m/s2 D. 2.5 m/s2

Understanding Concepts, continued Chapter 10 Standardized Test Prep Understanding Concepts, continued 1. A bicyclist traveling at 10 m/s applies her brakes, reducing her velocity to 5 m/s. If it takes 2 seconds to slow the bike, what is the acceleration during that period? A. –5 m/s2 B. –2.5 m/s2 C. 0 m/s2 D. 2.5 m/s2

Understanding Concepts, continued Chapter 10 Standardized Test Prep Understanding Concepts, continued 2. What happens to a moving object when the forces acting on it are exactly balanced? F. The object gradually slows and stops moving due to friction. G. The object moves at a constant speed, neither speeding up nor slowing down. H. The object accelerates because there is no friction to oppose the forces acting on it. I. The object accelerates because the force of gravity is stronger than friction.

Understanding Concepts, continued Chapter 10 Standardized Test Prep Understanding Concepts, continued 2. What happens to a moving object when the forces acting on it are exactly balanced? F. The object gradually slows and stops moving due to friction. G. The object moves at a constant speed, neither speeding up nor slowing down. H. The object accelerates because there is no friction to oppose the forces acting on it. I. The object accelerates because the force of gravity is stronger than friction.

Understanding Concepts, continued Chapter 10 Standardized Test Prep Understanding Concepts, continued 3. For which of the following is the velocity constant? A. a baseball traveling away from a bat after a hit B. a bicyclist on an oval track moving at a constant speed of 15 km/h C. a helicopter hovering motionless above a fixed point on the ground D. a canoe being carried down a winding river by a steady current

Understanding Concepts, continued Chapter 10 Standardized Test Prep Understanding Concepts, continued 3. For which of the following is the velocity constant? A. a baseball traveling away from a bat after a hit B. a bicyclist on an oval track moving at a constant speed of 15 km/h C. a helicopter hovering motionless above a fixed point on the ground D. a canoe being carried down a winding river by a steady current

Understanding Concepts, continued Chapter 10 Standardized Test Prep Understanding Concepts, continued 4. When describing the motion of an object, why do you need a reference point?

Understanding Concepts, continued Chapter 10 Standardized Test Prep Understanding Concepts, continued 4. When describing the motion of an object, why do you need a reference point? To describe the motion of an object, you need to compare the object’s position to a reference point to determine how the position is changing.

Understanding Concepts, continued Chapter 10 Standardized Test Prep Understanding Concepts, continued 5. A jet airplane must use a substantial amount of fuel to keep flying at a constant velocity. What two forces would change the velocity of the plane if the engines were shut off?

Understanding Concepts, continued Chapter 10 Standardized Test Prep Understanding Concepts, continued 5. A jet airplane must use a substantial amount of fuel to keep flying at a constant velocity. What two forces would change the velocity of the plane if the engines were shut off? Air resistance and the force due to gravity would change the velocity of the plane.

Chapter 10 Reading Skills Standardized Test Prep Reading Skills Read the passage below. Then, answer question 6. Some boats used in calm waters actually float on a cushion of air. A fan blows air below the hull of the craft, while another fan pushes air backward, propelling the boat forward. If the downward fan is turned off, the boat stops moving. The rear-facing fan cannot cause the boat to move until the other fan is turned on again.

Reading Skills, continued Chapter 10 Standardized Test Prep Reading Skills, continued 6. Demonstrate why the rear-facing fan can accelerate the boat when it is on a cushion of air, but not when it is in contact with the surface of the water.

Reading Skills, continued Chapter 10 Standardized Test Prep Reading Skills, continued 6. Demonstrate why the rear-facing fan can accelerate the boat when it is on a cushion of air, but not when it is in contact with the surface of the water. The boat experiences less friction when it is on a cushion of air than it does when it is in contact with the water. The rear-facing fan provides enough force to overcome only the lesser friction.

Interpreting Graphics Chapter 10 Standardized Test Prep Interpreting Graphics Base you answers to questions 7 and 8 on the graph below, which shows distance (m) versus time (s).

Interpreting Graphics, continued Chapter 10 Standardized Test Prep Interpreting Graphics, continued 7. What is the average speed of the runner whose motion is plotted on the graph? F. 1.0 m/s G. 1.8 m/s H. 2.0 m/s I. 4.5 m/s

Interpreting Graphics, continued Chapter 10 Standardized Test Prep Interpreting Graphics, continued 7. What is the average speed of the runner whose motion is plotted on the graph? F. 1.0 m/s G. 1.8 m/s H. 2.0 m/s I. 4.5 m/s

Interpreting Graphics, continued Chapter 10 Standardized Test Prep Interpreting Graphics, continued 8. During which interval is the runner’s average speed the greatest? A. 0 s to 5 s B. 5 s to 10 s C. 15 s to 20 s D. 20 s to 25 s

Interpreting Graphics, continued Chapter 10 Standardized Test Prep Interpreting Graphics, continued 8. During which interval is the runner’s average speed the greatest? A. 0 s to 5 s B. 5 s to 10 s C. 15 s to 20 s D. 20 s to 25 s