12.1 Forces

A man being pushed by the wind in the rain. The wind represents the force.

Figure 1 The wind pushes against the man and his umbrella. The push from the wind is a force.

A powerful storm is approaching. The weather forecast calls for gale-force winds. Many people in the city decide to leave work earlyin order to get home before things get worse. As shown in Figure 1, a man pushes ahead into a strong wind and shields himself from the driving rain with an umbrella. The strong wind makes it very difficult for him to hold onto his umbrella. To keep the umbrella from being pulled from his hands, he tightly squeezes the umbrella handle. Elsewhere, a store owner attempts to bring in a folding sign that hasn't blown awaybecause it is chained to a pole.

Wind is but one example of the many forces you experience every day. The study of forces is a very important part of physics. As you read this section you'll learn what forces are and how they make things move.

What Is a Force?

The man out in the storm is battling the forces of wind. A force is a push or a pull that acts on an object. A force can cause a resting object to move, or it can accelerate a moving object by changing the object's speed or direction. The force of the wind pushing against the man slows his speed. A strong gust could even change the direction in which he was moving.


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Table of Contents

Physical Science CHAPTER 1 Science Skills CHAPTER 2 Properties of Matter CHAPTER 3 States of Matter CHAPTER 4 Atomic Structure CHAPTER 5 The Periodic Table CHAPTER 6 Chemical Bonds CHAPTER 7 Chemical Reactions CHAPTER 8 Solutions, Acids, and Bases CHAPTER 9 Carbon Chemistry CHAPTER 10 Nuclear Chemistry CHAPTER 11 Motion CHAPTER 12 Forces and Motion CHAPTER 13 Forces in Fluids CHAPTER 14 Work, Power, and Machines CHAPTER 15 Energy CHAPTER 16 Thermal Energy and Heat CHAPTER 17 Mechanical Waves and Sound CHAPTER 18 The Electromagnetic Spectrum and Light CHAPTER 19 Optics CHAPTER 20 Electricity CHAPTER 21 Magnetism CHAPTER 22 Earth's Interior CHAPTER 23 Earth's Surface CHAPTER 24 Weather and Climate CHAPTER 25 The Solar System CHAPTER 26 Exploring the Universe Skills and Reference Handbook