Download Forces in Motion

Forces in Motion
Chapter 13
How can you
describe motion?
Lesson 1
• Velocity-describes the speed and the direction of an
object’s motion
Vocabulary
• Motion is all around you.
•
•
•
•
•
Steady, constant motion
Variable motion
Periodic motion
Circular motion
Vibrational motion
Types of Motion
• Average speed describes how far an object moves during
a certain amount of time.
Speed and Velocity
• The speed at which a person is moving can vary
according to which point of reference you use.
• Speed and velocity are NOT the same.
• Velocity describes the speed and the direction of an
object’s motion.
What are forces?
Lesson 2
• Force-a push or pull that acts on an object
• Work-when a force moves an object
• Power-the rate at which work is done.
Vocabulary
• When one object pushes or pulls another object, the first
object is exerting a force on the second one.
• Forces make a moving object speed up, slow down, or
change direction.
• Forces have both magnitude and direction.
• Magnitude is how strong a force is.
• Magnitude is measured in units called newtons (N).
Pushes and Pulls
• Every object in the universe exerts a gravitational pull on
every other object.
• Earth is strong enough to be felt—pulling objects toward
its center.
• Gravitational force determines an object’s weight.
Gravity
• Magnetism is the force that pushes and pulls on other
objects.
• Magnetic force is strongest at the poles.
• Every magnet has a north and south pole.
• Magnets are strongly attracted to iron, cobalt, nickel,
gadolinium.
• Opposites attract-Like poles repel
Magnetism and
Electricity
• Electric forces act between objects that are electrically
charges.
• Electric charge comes from gain or loss of electrons.
• An object that looses electrons is negatively charged.
• An object that gains electrons is positively charged.
• Gravity, Magnetic, and electric forces can act between
objects.
Gravity, Electricity, and
Magnetism
• The force that results when two materials rub against
each other is called friction.
• Acts to slow down the motion of an object.
Friction
• Work is done when a force moves an object.
Work and Power
• Work is measured in joules (J).
• Power is the rate of work being done.
What are
Newton’s laws of
motion
Lesson 3
• Equilibrium-when all the forces acting on it balance each
other.
• Inertia-the tendency of an object to resist any change in
motion.
• Acceleration-the rate at which the velocity of an object
changes over time.
Vocabulary
• Different forces can act on an object at the same time.
• The combination of these forces is the net force on the
object.
• The net force determines whether the object will move or
stop.
• When the forces on an object are opposite directions, they
are balance, in a state of equilibrium
Net Forces
• An object at rest stays at rest until a net force acts on it.
An object moving at a constant speed will continue to
move in a straight line and at a constant speed.
• Inertia is when an object will resist a change in motion.
Newton’s First Law
• The net forces acting on an object can change an object’s
velocity by causing it to speed up, slow down, or change
direction.
• The changes in velocity is acceleration.
Newton’s Second Law
• When one object exerts a force on a second object, the
second object exerts a force on the first object. (Actionreaction law of motion)
Newton’s Third Law
What are simple
machines?
Lesson 4
• Machine-a device that changes the direction or the
amount of force needed to do work.
Vocabulary
• Work is done when a force causes an object to move.
• A machine is used to do work., not eliminate work, but
make it easier.
• Simple machines only have a few parts.
• Levers, wheel and axels, pulleys, and inclined planes are
simple machines.
Machines and Work
• Consists of a rope of cable that runs through a grooved
wheel.
• Makes it easier to lift an object.
Pulley
• Made up of a circular object and a shaft.
• Changes the direction of force from circular to a straight
line.
Wheel and Axel
• A stiff bar rotates abound a fixed point called a fulcrum.
Lever
• Consists of a flat surface with one end higher than the
other.
Inclined Planes
• A machine becomes complex when it uses two or more
simple machines.
Complex Machines