Question

The angle between force $\vec { F } = ( 3 \hat { i } + 4 \hat { j } - 5 \hat { k } )$ unit and displacement $\overrightarrow { \mathrm { d } } = ( 5 \hat { \mathrm { i } } + 4 \hat { \mathrm { j } } + 3 \hat { \mathrm { k } } )$ unit is :

• A. $\cos ^ { - 1 } ( 0.16 )$
• B. $\cos ^ { - 1 } ( 0.32 )$
• C. $\cos ^ { - 1 } ( 0.24 )$
• D. $\cos ^ { - 1 } ( 0.64 )$

Answer 1

Answer: (B)

$\cos ^ { - 1 } ( 0.32 )$

Answer 2

Here,

unit

$\therefore | \overrightarrow { \mathrm { F } } | = \sqrt { ( 3 ) ^ { 2 } + ( 4 ) ^ { 2 } + ( - 5 ) ^ { 2 } } = \sqrt { 50 }$ unit

$| \overrightarrow { \mathrm { d } } | = \sqrt { ( 5 ) ^ { 2 } + ( 4 ) ^ { 2 } + ( 3 ) ^ { 2 } } = \sqrt { 50 }$ unit

Let $\theta$be angle between .

or $\theta = \cos ^ { - 1 } ( 0.32 )$