Measuring Motion What is a frame of reference

Measuring Motion

• What is a frame of reference? – A system for specifying the precise location of objects in space and time. • What is Displacement? • What is Distance? • The change of an object’s position. – Distance measures the path taken.

Observing Motion • • Distance measures the path taken. Displacement is the change of an object’s position. – displacement: the change in position of an object – always includes direction • In the diagram: – yellow line = distance – black arrow = displacement

Displacement (cont. ) The displacement or change in position of an object is a vector quantity that can be calculated by subtracting the initial position from the final position ◦ Δx = xf – xi ◦ vector properties have magnitude and direction ◦ Displacement can be positive or negative depending upon the direction of motion.

• What is motion? – The state in which one object’s distance from another is changing • How can you tell that an object is in motion? – If one objects’ distance from another object is changing. • Is there anything in motion in this classroom?

Reference Point • Reference Point – A place or object used for comparison to determine if something is in motion • • **An object is in motion if it changes position relative to a reference point. This school is moving relative to what reference points? – The North pole – The Sun – Any other planet – Other galaxies, etc.