In Motion:A Physics Unit

I love physics, but I hate moving.

· Work with both vector and scalar quantities

· Describe differences of distance and displacement

· Recognize interval and instant

· Describe differences of speed and velocity

Velocity Speed Displacement

Position Distance Origin

∆ (delta) Scalar Vector

Instant Interval

Key Words

To describe movement you must have two things:

Origin Position

Origin – a reference (start) point, where we begin to take measurements from.

Position – the location an object is found away from the Origin.

Distance is the total travel of the object, regardless of the path or direction.

Δd = 3 cm

Origin Position

It is a scalar value - it is given only as a number for its size with a unit.

Displacement is the overall change in position of an object.

It is a vector quantity and must be given with a number for its size, a unit and a DIRECTION.

∆d = 3 cm

Origin Position

+

The formula for Displacement is found by the final position minus the initial position

A change in any quantity is found by final minus initial values.

∆d = d2 - d1

initial position (origin)

final position delta means “change in”

vector

A toy car begins at -1 cm. If the car stops at +3 cm, calculate the distance and displacement of the car.

d1 = -1 cm d2 = +3

Position

∆d = 4 cm +

Δd = 4 cm

Origin

∆d = d2 - d1

∆d = (+3) - (-1)

Draw a number line to show a car moving from a start of +2 cm and stops at the -3 cm mark. Find the displacement of the car.

Origin Position

∆d = 5 cm -d1 = +2 cm d2 = -3

∆d = d2 - d1

∆d = (-3) - (+2)

If you walked around this block, what would your Distance be?

∆d = 100 m10

0 m

100 m

100 m

Δd = 300m

Your Displacement would be?

[East]10

0 m

100 m

100 m

Instants and Intervals of Time

In physics, Time occurs two ways:

An instant of time is a reading at a particular, precise moment.

An interval of time is total amount of time between two instants.

Interval = instant2 - instant1

∆t = t2 - t1

Instant or interval of time is a SCALAR quantity.

scalar

“change in”Interval

final instant

initial instant

d = d2 - d1

t = t2 - t1