1. Last week … Position, velocity, acceleration - The position of an object is the location of the center of the object. The position of a person is a point between the eyes. -Velocity is the rate of change in position. Velocity describes how f ast something moves. -Acceleration describes how fast does fast change. Acceleration describes how rapidly an object is speeding up. Acceleration the rate of change of the velocity.

2. Force Context: Move the cart. Move the car. Throw the ball. Definition: -A force is a push, a pull, or a lift. -A force is a tendency for change. -A force makes a mass accelerate, if friction is small. Examples: Weight force, tension in a string, spring force, pressure,spring forcepressure electric forceelectric force (alternating),alternating magnetic forcemagnetic force (between a current and a magnet,between a current and a magnet between two currentsbetween two currents), nuclear forces

3. Newton first Law Context: Taking the Aristotelian idea of "natural states", the condition of constant velocity whether it be zero or nonzero is now considered the "natural state" of all massive objects. Definition: Newton’s first law states that objects move with constant velocity unless there is an unbalanced external force. Discussion: -Friction is often an unbalanced force. -If an object stays at rest, if there is no net force. -If it is at rest (in equilibrium), the net force is zero. Lecture demos: Teddy bear on cartTeddy bear on cart, table cloth and dishestable cloth and dishes

4. Newton’s second law Context: How hard do I have to push, to make a car move? Definition: Newton’s second law states Force = mass * acceleration, -i.e. F=ma. Discussion: The intuitive Aristotelian belief that a net force is required to keep an object moving with constant velocity (therefore zero acceleration) is objectively wrong. - In many real world friction is the only force acting on the object. Then the net force is not zero, and the object decelerates. Though Sir Isaac Newton's most famous equation is F=ma.Sir Isaac NewtonF=ma Lecture demo: Sling shotSling shot, rocket chairrocket chair

5. Newton’s third law Context: Pushes are equal and opposite. Definition: Newton’s third law states that all forces between two objects occur in pairs, and these two forces are equal in magnitude and opposite in direction. Discussion: To every action there is always opposed an equal reaction: or the mutual actions of two bodies upon each other are always equal, and directed to contrary parts. — Whatever draws or presses another is as much drawn or pressed by that other. If you press a stone with your finger, the finger is also pressed by the stone. Newton's third law. The skaters' forces on each other are equal in magnitude, and in opposite directions Lecture demos: Rope and skate boards, Masses and springs

6. Force, Equilibrium & Newton’s Laws Force = push or pull. An object is in equilibrium if it is at rest and the net force is zero. Newton’s first law: An object moves with constant velocity if the net force is zero. An object moves stays at rest if the net force is zero. Newton’s second law: The acceleration of an object is equal to the net force divided by the mass, -i.e. Force = mass * acceleration. Newton’s third law: Forces between two objects are equal in magnitude and opposite in direction.