A partical has the position vector ` r = hati - 2 hatj + hatk ` and the linear momentum ` p = 2 hati - hatj + hatk ` its angular momentum about the origin is

Options

A. `-hati+hatj-3hatk`
B. `-hati+hatj+3hatk`
C. `hati+hatj+3hatk`
D. `hati-hatj-5hatk`

Answer

B

Explanation

Angular momentum, L = ` r xx p `
` = |{:(hati,,hatj,,hatk),(1,,-2,,1),(2,,-1,,1):}| `
` = hati ( -2 + 1 ) - hatj ( 1 - 2 ) + hatk ( - 1 + 4 ) `
` = - hati + hatj + 3 hatk `