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## PowerPoint Slideshow about ' Force and Laws of Motion' - magee-berger

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Force

1 N= 0.225lbs

- A push or pull on an object.
- Can change the motion of an object
- Measured in Newtons (N) (kg*m/s2)
- Friction and gravity are examples.

- Friction
- A force that acts against motion.
- Between objects that are touching
- Between the legs of a desk and the floor when you push a desk

Gravity

- A force that pulls matter together
- Between objects that are not touching
- Isaac Newton
- “the force of gravity acts between all objects in the universe”
- Gravity exists between all matter
- Gravity exists between you and your pencil however it is very weak
- The more mass an object has, the stronger its gravity
- Keeps objects in orbit around a star, planet or moon.
- Makes objects “fall”

Combining Forces

Force Diagrams:

- We use arrows to show the different forces acting on objects
- Direction of arrow shows the direction the force is acting
- Length of the arrow shows the strength (size or magnitude) of the force
- Net force: the combination of all forces acting on an object

5N

=

= 10N

5N

5N

10N

=

5N

5N

5N

=

0 N

Balanced Forces

- When two forces are the same strength (magnitude or size) but acting in opposite directions on a the same object.
- Cannotchange an objects motion (speed and direction)
- An object at rest to start with balanced forces will continueat rest
- An object moving at 30 mph to the left with balanced forces acting on it will continue to move at 30 mph to the left

- Forces are equal
- Motion remains the same
- If not moving, it continues to not move
- If moving , it continues to move exactly the same

Forces on the person are balanced: Gravity pulls down on person, chair pushes up on person

10 N

10 N

Unbalanced Forces

- Will change an objects motion (speed and direction)
- A net force results.
- Net force is calculated by adding forces in the same direction or subtracting forces in opposite directions
- If an object is starting at restwhen a net force of 40 N is applied, the object will move to the right
- If an object is already moving to the right at a constant speed when a net forceof 40 N is applied, the object will speed up.

- Net force of 40 N to the Right
- 40 N
- New motion depends on the starting motion

Newton’s 1st Law of Motion

Law of Inertia

- Object at rest will remain at rest
- Object in motion will continue in motion in a straight line

- The tendency of an object to resist a change in motion.
- The higher the mass of an object , the higher its inertia is.

Unless an unbalanced force acts upon it

Circular motion animation

car making a sharp turn

Newton’s 2nd Law of Motion

- F = MA
- The larger the net force on an object , the more the objects motion will change (greater acceleration).
- Objects with larger masses, need more force to change their motion.

Newton’s 3rd Law of Motion

- When one object exerts a force on another object, the second object exerts an equal but opposite force on the first object
- They are not balanced forces because the forces act on different objects

100 N

100 N

Newton’s 3rd Law

- Action-Reaction
- For every action (force), there is an equal but opposite reaction (force)

3 laws Video clip

Newton’s 3 Laws

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