Force and Motion

Mass The amount of matter something has Measured in kilograms (kg) Inertial mass is a quantitative measure of an object's resistance to changes in velocity. Gravitational mass is a quantitative measure that is proportional to the magnitude of the gravitational force

Motion A change in position relative to a reference time Distance – entire path travelled or how far an item has moved from its starting point as an accumulative value Measured in meters Displacement – distance and direction of the objects final position to its initial position Vectors are used to represent the size and direction of displacement

How fast something is moving per unit of time Can be measured in two ways Instantaneous – given moment (radar) Average – how quickly an object moved over the entire distance (calculated) Distance travelled / time Measured in meters/second (m/s)

Speed and direction of motion Distance / time with direction 5 m/s, north 5 m/s (vectors can be used to show direction)

Forces A push or pull on an object by another object Cause of acceleration Measured in Newtons (N) Forces video

Friction Type of force that opposes a moving object Depends on the roughness of a surface

Acceleration Change in velocity over a period in time Positive – speeding up Negative – slowing down Calculated by (final velocity – initial velocity) / (Final time - initial time) Measured in m/s2

Type of acceleration Created when two large objects are attracted to each other The earth’s pull on an object 9.81 m/s2

Newton’s laws of motion Intro rap

Newton’s 1st law of motion Inertia An object moving in a straight line will continue to move in a straight line unless acted upon by another force An object will stay at rest unless acted upon by another force

Newton’s 1st law of motion Examples: When riding a horse, the horse suddenly stops and you fly over its head The magician pulls the tablecloth out from under a table full of dishes 1st law video

Newton’s 2nd law of motion Focuses on the relationship between mass, acceleration and force of an object Force = mass x acceleration Measured in – Newtons (N) = kg X m/s2 In a vehicle, the net external force on a passenger's body is the mass of the vehicle multiplied by its acceleration, so what happens to the person without a seatbelt? Importance of seatbelt

Newton’s 3rd law of motion When one body exerts a force on a second body, the second body simultaneously exerts a force equal and opposite in direction to that of the first body Examples Guns being fired - why they kick in proportion to the size of the bullet Walking Billiards Jumping out of a boat onto the dock

Review Newton’s 3 laws of motion

Momentum = mass X velocity P = MV Increases when the mass or velocity increases An object at rest does not have momentum, no matter how large it is. Momentum and inertia are not the same

Conservation of momentum The total momentum of two objects before the collision is equal to the total momentum of the two objects after the collision

Conservation of momentum If one ball stops dead after the collision, the other ball will continue away with all the momentum. If the moving ball continues or is deflected then both balls will carry a portion of the momentum from the collision

Roller Coasters Kinetic and potential energy in a roller coaster Roller coaster video Roller coaster simulation