Explain the First Law of
Motion
• An object will not change its motion unless a force acts on it.
• An object that is not moving remains at rest until something pushes or pulls it.
• An object that is moving remains moving until something pushes or pulls it.

Explain the First Law of
Motion
• The force that causes objects to slow down is FRICTION.
• Friction always acts opposite to the direction of motion.
• To keep an object moving when friction is acting on it, you have to keep pushing or pulling on the object to overcome the frictional force.

Explain the First Law of
Motion
• All objects resist having their motion changed.
• This tendency to resist a change in motion is called inertia.
• The more mass an object has,
the greater its inertia.

See Examples of the 1 st Law of Motion Here: http://www.jracademy.com/~m basteaf/newton/first/index.ht
ml

Review the First Law here: http://www.usoe.k12.ut.us/cur r/science/sciber00/8th/forces
/sciber/newtons.htm

More information about
Newton’s First Law of
Motion may be found here: http://www.beyondbooks.com/ psc91/4a.asp

Explain the Second Law of
Motion
• A change in motion occurs only if a net force is exerted on an object.
• A net force changes the velocity of the object, and causes it to accelerate.

Explain the Second Law of
Motion
• If an object is acted upon by a net force, the change in velocity will be in the direction of the net force.
• Acceleration can be calculated from the formula:

Explain the Second Law of
Motion
• The acceleration of an object depends on its mass.
• The more mass an object has or the more inertia it has, the harder it is to accelerate .
• More mass means less acceleration if the force acting on the objects is the same.

Explain the Second Law of
Motion
• If a stands for the acceleration,
Fnet for the net force, and m for the mass, this formula can be written as follows:
• In this formula the force is in newtons, the mass is in kilograms, and the acceleration is in meters per second squared.

See Examples of the 2 nd Law of Motion Here: http://www.jracademy.com/~m basteaf/newton/second/index.
html

Review the Second Law here: http://www.usoe.k12.ut.us/cur r/science/sciber00/8th/forces
/sciber/newton2.htm

More information about
Newton’s Second Law of
Motion may be found here: http://www.beyondbooks.com/ psc91/4d.asp

Explain the Third Law of
Motion
• When one object exerts a force on a second object, the second object exerts an equal force in the opposite direction on the first object.
• The force exerted by the first object is the action force.
• The force exerted by the second object is the reaction force.

See Examples of the 3 rd Law of Motion Here: http://www.jracademy.com/~m basteaf/newton/third/index.ht
ml

Review the Third Law here: http://www.usoe.k12.ut.us/cur r/science/sciber00/8th/forces
/sciber/newton3.htm

More information about
Newton’s Third Law of
Motion may be found here: http://www.beyondbooks.com/ psc91/4f.asp