Motion and Speed. Motion Definition: When an object changes its position relative to a reference point Distance – How far an object has moved. Displacement.

Motion and Speed

Motion

• Definition: When an object changes its position relative to a reference point

• Distance – How far an object has moved.

• Displacement – Distance and direction of an object’s change of position from a starting point.

Speed

• Definition: Distance an object moves in a certain period of time.

• Rate – Any change over time.

• Formula for calculating Average Speed:

Total Distance (km)

Total Time (hr or sec or min)

Vectors

• Definition: A quantity that has both a magnitude (an amount) and a direction.

• Two examples– Velocity (v)– Acceleration (a)

Velocity

• Definition: Speed and direction of an object’s motion.

Acceleration

• Definition: Change in velocity’s rate

• Formula:

Change in Velocity

Time

Acceleration

• Acceleration = Change in velocity / time• Change in velocity (v) =

Final Velocity – Initial Velocity

• SI unit (derived) = m / s2

• Two types:- Positive: positive slope- Negative: negative slope

Determining Acceleration from a Graph

Determining Acceleration from a Graph

Force

• Definition: A push or pull that one body applies to another.

• A force can cause an object’s motion to change

• When two forces combine, they create a net force.

• Balanced force are equal in size and opposite in direction.

• Unbalanced force are unequal and/or not in the same direction.

Inertia and Mass

• Inertia – an object’s resistance to any change in motion

• Inertia – an object’s tendency to stay at rest or in motion

• Object with greater mass have greater inertia

Newton’s First Law of Motion

• AKA, Principle of Inertia

• Two conditions:– an object moving at a constant velocity keeps

moving at that velocity unless a net force acts on it

– an object at rest will stay at rest unless a net force acts on it.

Examples of inertia

• A passenger not wearing a seat belt keeps moving forward at the car’s speed after the car stops.

• Harder for a semi to stop than a car.

• Astronaut space walk.