2.1 D ESCRIBING MOTION IN A STRAIGHT LINE Forces and Motion Physics 2AB

S CALARS A scalar quantity is a quantity that has magnitude only and has no direction in space Examples of Scalar Quantities:  Length  Area  Volume  Time  Mass

V ECTORS A vector quantity is a quantity that has both magnitude and a direction in space Examples of Vector Quantities:  Displacement  Velocity  Acceleration  Force

V ECTOR D IAGRAMS Vector diagrams are shown using an arrow The length of the arrow represents its magnitude The direction of the arrow shows its direction

R EPRESENTING V ECTORS Vectors are represented using special vector notation Vector are denoted in the text book as bold (pg 56) e.g. s 1 + s 2 On paper we use a half arrow above the letter e.g.

Vectors in opposite directions: 6 m s m s -1 =4 m s -1 6 N10 N=4 N A DDING V ECTORS Vectors in the same direction: 6 N4 N=10 N 6 m =10 m 4 m AAdding vectors requires consideration of both magnitude and d irection

Vectors in opposite directions: 6 m s m s -1 = -6 N10 N = S UBTRACTING V ECTORS Vectors in the same direction: 6 N 4 N = 6 m = 4 m SSubtracting vectors can be thought of as a dding negative vectors 2 N 2 m 16 m s N

M ULTIPLYING V ECTORS s 1 -3N  Vectors can be multiplied by scalar quantities  Multiplying by a positive term will change the magnitude but the direction will remain the same  Multiplying by a negative term will change the magnitude and the direction will be reversed +ve -ve +ve -ve 2 s 1 = 2 (-3) = - 6N = 6N to the left -3 s 1 = -3 (-3) = 9N = 9N to the right

V ECTORS IN 2D ( NEEDED FOR 3AB) Example Eric leaves the base camp and hikes 11 km, north and then hikes 11 km east. Determine Eric's resulting displacement. = √( ) = √(242) = 15.6 km Ө= tan-1 ( ) = 45° R = 15.6 km N45 °E |R|

V ECTOR EXAMPLE PROBLEMS If s 1 is 12 m east and s 2 is 8 m west, determine: 1. s 1 + s 2 2. s 1 – s 2 3. s s s 1 12 m E 8 m W N