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Newton’s Laws. Newton’s First Law of Motion “Every object continues in its state of rest, or...

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Newton’s Laws
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Page 1: Newton’s Laws. Newton’s First Law of Motion “Every object continues in its state of rest, or of uniform motion in a straight line, unless it is compelled.

Newton’s Laws

Page 2: Newton’s Laws. Newton’s First Law of Motion “Every object continues in its state of rest, or of uniform motion in a straight line, unless it is compelled.

Newton’s First Law of Motion

• “Every object continues in its state of rest, or of uniform motion in a straight line, unless it is compelled to change that state of motion by forces impressed upon it ”

• The tendency of matter to maintain its state of motion is known as INERTIA.

Page 3: Newton’s Laws. Newton’s First Law of Motion “Every object continues in its state of rest, or of uniform motion in a straight line, unless it is compelled.

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.

Page 4: Newton’s Laws. Newton’s First Law of Motion “Every object continues in its state of rest, or of uniform motion in a straight line, unless it is compelled.

Newton’s First Law of Motion

• Changes in motion do not happen spontaneously.

• Example: 1) Tablecloth under dishes

Page 5: Newton’s Laws. Newton’s First Law of Motion “Every object continues in its state of rest, or of uniform motion in a straight line, unless it is compelled.

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.

Page 6: Newton’s Laws. Newton’s First Law of Motion “Every object continues in its state of rest, or of uniform motion in a straight line, unless it is compelled.

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”

Page 7: Newton’s Laws. Newton’s First Law of Motion “Every object continues in its state of rest, or of uniform motion in a straight line, unless it is compelled.

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).

Page 8: Newton’s Laws. Newton’s First Law of Motion “Every object continues in its state of rest, or of uniform motion in a straight line, unless it is compelled.

Action at a Distance Forces…

• 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).

Page 9: Newton’s Laws. Newton’s First Law of Motion “Every object continues in its state of rest, or of uniform motion in a straight line, unless it is compelled.

Contact and Field Forces

Page 10: Newton’s Laws. Newton’s First Law of Motion “Every object continues in its state of rest, or of uniform motion in a straight line, unless it is compelled.

How Many FUNDAMENTAL Forces?

• Four• Strong Nuclear Force • Electromagnetic Force• Weak Nuclear Force• Gravitational Force

Page 11: Newton’s Laws. Newton’s First Law of Motion “Every object continues in its state of rest, or of uniform motion in a straight line, unless it is compelled.

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

Page 12: Newton’s Laws. Newton’s First Law of Motion “Every object continues in its state of rest, or of uniform motion in a straight line, unless it is compelled.

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

Page 13: Newton’s Laws. Newton’s First Law of Motion “Every object continues in its state of rest, or of uniform motion in a straight line, unless it is compelled.

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

Page 14: Newton’s Laws. Newton’s First Law of Motion “Every object continues in its state of rest, or of uniform motion in a straight line, unless it is compelled.

Example

When the ball at the end of the string swings to its lowest point, the string is cut by a sharp razor. Which path will the ball then follow?

Page 15: Newton’s Laws. Newton’s First Law of Motion “Every object continues in its state of rest, or of uniform motion in a straight line, unless it is compelled.

Example: Answer (b)

When the ball at the end of the string swings to its lowest point, the string is cut by a sharp razor. Which path will the ball then follow?

Answer: Inertia

Page 16: Newton’s Laws. Newton’s First Law of Motion “Every object continues in its state of rest, or of uniform motion in a straight line, unless it is compelled.

Example

When the pellet fired into the spiral tube emerges, which path will it follow? (Neglect gravity).

Page 17: Newton’s Laws. Newton’s First Law of Motion “Every object continues in its state of rest, or of uniform motion in a straight line, unless it is compelled.

Example: Answer (b)

When the pellet fired into the spiral tube emerges, which path will it follow? (Neglect gravity).

Answer: Inertia


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