Newton’s 1 st Law. Newton’s First Law of Motion Objects in motion will to stay in motion,...
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Transcript of Newton’s 1 st Law. Newton’s First Law of Motion Objects in motion will to stay in motion,...
Newton’s First Law of Motion
• Objects in motion will to stay in motion, objects at rest will stay at rest unless they are acted upon an outside force
• The tendency of matter to maintain its state of motion is known as INERTIA.
Newton’s First Law of Motion
• Inertia prevents an object at rest from moving spontaneously or an object in uniform linear motion from changing its speed or direction spontaneously.
• Force is simply a push or a pull.
Newton’s First Law of Motion
Inertia is the tendency of an object to resist changes in its velocity: whether in motion or motionless. These pumpkins will not move unless acted on
by an unbalanced force.
Forces
• Usually think of a force as a push or pull• Vector quantity• May be a contact force or a field force
• Contact forces result from physical contact between two objects
• Field forces act between disconnected objects• Also called “action at a distance”
Contact Forces…
• Contact forces are forces which exert a push or pull (interact) while touching.
• Examples:• frictional forces, • tensional forces, • air resistance forces, • applied forces (e.g., pushes or pulls).
Action at a Distance Forces…
• Field Force or Action-at-a-distance forces exert a push or pull (interact) without physical contact.
• Examples:• Gravity (e.g., when you jump off the
ground, there is still a gravitational pull between you and the Earth),
• Electric (e.g., static electricity), • Magnetic (e.g., two magnets).
How Many FUNDAMENTAL Forces?
• Four• Strong Nuclear Force • Electromagnetic Force• Weak Nuclear Force• Gravitational Force
What do they DO?
• Strong Nuclear Force• Holds nucleus together
• Electromagnetic Force• Interaction of electric & magnetic fields
• Weak Nuclear Force• Causes radioactivity
• Gravitational Force• Attracts mass
How Strong are they?
• On a relative scale, we let the strong force = 1, then…
• Strong Nuclear 1.00• Electromagnetic 1 x 10-2 • Weak Nuclear 1 x 10-13
• Gravitational 1 x 10-38
So just how strong is gravity compared to the force that holds the atoms nucleus together?
External and Internal Forces
• External force• Any force that results from the interaction
between the object and its environment• Internal forces
• Forces that originate within the object itself• They cannot change the object’s velocity
Example
When the pellet fired into the spiral tube emerges, which path will it follow? (Neglect gravity).