Everything Science Grade 10

21.2 CHAPTER 21. MOTION IN ONE DIMENSION

Position ESAGU

DEFINITION: Position

Position is a measurement of a location, with reference to an origin.

Quantity: Position (x) Unit name: metre Unit symbol: m

A position is a measurement of a location within a reference frame. This means that posi-
tions can be negative or positive depending on the choice for the reference frame’s coordi-
nate system. See video: VPgmf at http://www.everythingscience.co.za

Depending on which reference point we choose, we can say that the school is 300 m from
Kosma’s house (with Kosma’s house as the reference point or origin) or 500 m from Kevin’s
house (with Kevin’s house as the reference point or origin).

100 m^100 m 100 m^100 m^100 m 100 m

School Komal Kholo Kosma Kogis Kevin Shop

The shop is also 300 m from Kosma’s house, but in the opposite direction as the school.
When we choose a reference point, we have a positive direction and a negative direction.
If we choose the directiontowards the schoolasnegative, then the direction towards the
shop is positive. A negative direction is always opposite to the direction chosen as positive.

− 300 − 200 − 100 0 +100 +200 +300

School

Kosma’s house

(reference point) Shop

x(m)

The origin is at Kosma’s house and the position of the school is− 300 m. Positions towards
the left are defined as negative and positions towards the right are defined as positive.

Note that we could also choose thepositivedirection to betowards the school. In this case
Kosma’s house is still 300 m away from the school, but it is now in the positive direction.

390 Physics: Mechanics