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CHAPTER THIRTEEN

CHAPTER THIRTEEN. FORCES IN MOTION. How Can You Describe Motion?. Objects move in many different ways and ad varying rates of speed. There are different kinds of motion: constant, variable, periodic, circular, and vibrational .

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CHAPTER THIRTEEN

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  1. CHAPTER THIRTEEN FORCES IN MOTION

  2. How Can You Describe Motion? • Objects move in many different ways and ad varying rates of speed. • There are different kinds of motion: constant, variable, periodic, circular, and vibrational. • Average speed describes how far an object moves during a certain amount of time. It is calculated using the following formula: • Average Speed = Distance/Time

  3. How Can You Describe Motion? • Motion is always measured in relationship with some location called a point of reference. • Velocity describes the speed and direction of an object’s motion.

  4. What Are Forces? • A force is a push or a pull that acts on an object. Force is measured in Newtons. • Forces have both magnitude and direction. • Every object in the universe exerts a gravitational force on every other object. • Magnetism is a force that pushes and pulls on objects.

  5. What Are Forces? • Magnets exert magnetic force on objects made of iron and certain other elements. • An object is electrically charged when it gains or loses electrons. • Gravity differs from magnetism and electricity in that it cannot be blocked, and gravity acts only to pull objects, not to push them, while magnetism and electricity can both push and pull.

  6. What Are Forces? • Friction is the force that results when two materials rub against each other. • Friction slows down the motion of an object or prevents it from moving. • Unlike other forces, friction depends on qualities of the objects that are pushing or pulling against one another.

  7. What Are Forces? • Work is done when a force moves an object. It is measured in Joules. • Force x Distance = Work • Power is the rate at which work is done. It is measured in Watts. • Work/Time = Power

  8. What Are Newton’s Laws of Motion? • All forces acting on an object make up the net force. When all the forces acting on an object balance, the object is in a state of equilibrium. • Newton’s first law of motion says that an object at rest stays at rest, and an object moving in a straight line at a constant speed will continue to move in a straight line and at constant speed until a net force acts on the object.

  9. What Are Newton’s Laws of Motion? • The tendency of an object to resist any change in motion is known as inertia. • Inertia is influenced by mass: objects with greater mass have greater inertia than objects with lesser mass. • Newton’s second law of motion describes the relationship between acceleration (the rate at which an object’s velocity changes over time), mass, and net force.

  10. What Are Newton’s Laws of Motion? • The net forces acting on an object change its velocity by causing it to speed up, slow down, or change direction, all of which are referred to as acceleration. • The stronger the force acting on an object, the more it will accelerate, as described by the formula: • Force = Mass x Acceleration

  11. What Are Newton’s Laws of Motion? • Newton’s third law of motion states that when on object exerts a force on another object, the second object exerts a force on the first object. • Action-reaction forces are always equal and opposite, and they always occur in pairs.

  12. What Are Simple Machines? • Machines change the direction or the amount of force required to do work. • Simple machines have only a few parts. A pulley and a wheel and axle are two types of simple machines. • A lever is a simple machine in which a stiff bar rotates around a fixed point called a fulcrum. • An inclined plane is a simple machine consisting of a flat surface with one end higher than the other.

  13. What Are Simple Machines? • A screw, a doorstop, and a ramp are modifications of the inclined planes that make work easier. • A machine that uses two or more simple machines is called a complex machine. • A complex machine may use forces such as gravity, magnetism, human force, burning fuel, or electricity to operate each of the simple machines within it.

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