Page 238 - Class-11-Physics-Part-1_Neat

212 PHYSICS

Let a, b and c be arbitary vectors with
a × b = ab sin θ
magnitudes a, b and c. Then
ˆ
a × (b + ) c = ( a b× ) ( a+ × ) c i ˆ ˆ j k
s
s
×
×
( a) b = a × ( b) = s (a b) (s is a scalar) a × b = − b × a = a x a y a z
b b b
x y z
Let θ be the smaller of the two angles = (a b − b a i ˆ (a b − b a j ˆ (a b − b a ) k
ˆ
) +
) +
between a and b. Then y z y z z x z x x y x y
a . (b × c) = b . (c × a) = c . (a × b)
a ⋅ b = b ⋅ a = a x b + a y b + a z b = ab cos θ
x
z
y
a × (b × c) = (a . c) b – (a . b) c
APPENDIX A 6
SI DERIVED UNITS
A 6.1 Some SI Derived Units expressed in SI Base Units

2018-19