Newton's 1st and 3rd laws of motion 8.P.2A.3: Construct explanations for the relationship between the mass of an object and the concept of inertia (Newton’s First Law of Motion). 8.P.2A.4: Analyze and interpret data to support claims that for every force exerted on an object there is an equal force exerted in the opposite direction (Newton’s Third Law of Motion).

Newton’s 1st law of motion Newton’s First Law states, “The velocity of an object will remain constant unless a net force acts on it.” It is called the Law of Inertia. If an object is moving, it will continue moving with a constant velocity (in a straight line and with a constant speed) unless a net force acts on it. If an object is at rest, it will stay at rest unless a net force acts on it.

Inertia is the tendency of the motion of an object to remain constant in terms of both speed and direction. The amount of inertia that an object has depends on the object’s mass. The more mass an object has the more inertia it has. Any object that has mass, has inertia!

If an object has a large amount of inertia (due to a large mass) It will be difficult to slow it down or speed it up of it is moving. make it start moving if it is at rest. make it change direction.

Inertia is the reason that it is impossible for vehicles to stop instantaneously. Inertia is the reason that it is harder to start pushing a cart full of items than to start pushing an empty cart.

DO NOT WRITE The objects on the table have inertia and want to remain at rest as the tablecloth is pulled out beneath them.

Newton’s 3rd law of motion Newton’s Third Law of Motion states, “When one object exerts a force on a second object, the second one exerts a force on the first that is equal in magnitude and opposite in direction.” This law is called the “Law of Action and Reaction”.

Even IF the forces are equal in magnitude and opposite in direction, they do not cancel each other. Each object is exerting one force on the other object. Each object is experiencing only one force.

The action and reaction forces are reciprocal on an object. Action force is pushing down on the trampoline Reaction force is the trampoline pushing back

Steam powered vehicle circa 1891 Action force steam exiting at C Reaction force forward motion

Identify the action and reaction forces shown