Question

A particle moves on a straight line with a uniform velocity. Its angular momentum
(a) is always zero
(b) is zero about a point on the straight line
(c) is not zero about a point away from the straight line
(d) about any given point remains constant.

Answer 1

Answer ⇒ Option (b), Option (c), and Option (d) .

Explanation ⇒ The angular momentum of a particle about a point will be given by the Relation,

Angular Momentum = mvr

where r is the perpendicular distance of the line of velocity from the point,

Since for a point on the line, r will be equal to the 0, and for a point away from the line, r is not zero.

Hence (b) and (c) is correct.

Also, for a given point r will be constant.

Hence Option (d). is also correct.

Hope it helps.

Answer 2

HEY!!

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⏩⏩Option "b", "c" and "d" are correct.

✴"b" is zero about a point on the straight line.

⚫Angular momentum = m(r⃗ ×v⃗ )

✔If the point is on the straight line, r⃗ and v⃗  are having same direction then their cross product will be zero. Angular momentum is zero.

✴"c" is not zero about a point away from the straight line.

✔If the point is not on the straight line, r⃗ and v⃗  are not having the same direction then the cross product will not be zero. Angular momentum is non-zero.

✴"d" about any given point remains constant.

✔It's angular momentum about any given point remains constant because no external torque is applied on the body.