A dimensionless quantity
(a) never has a unit, (b) always has a unit,
(c) may have a unit, (d) does not exist.

Question

A dimensionless quantity
(a) never has a unit, (b) always has a unit,
(c) may have a unit, (d) does not exist.

maheshmeghwal9 · Answer

Please give example too.

turingtest · Answer

radians are dimensionless because they are defined in terms of length/length
(circumference/diameter)

turingtest · Answer

$$\pi\text{ radians }={C\cancel{\text{ meters}}\over d\cancel{\text{ meters}}}$$so the units cancel

maheshmeghwal9 · Answer

thanx i gt it 
but wt about this plz?
this is last one!

A unitless quantity
(a) never has a nonzero dimension,
(b) always has a nonzero dimension,
(c) may have a nonzero dimension,
(d) does not exist.

turingtest · Answer

if it is unitless then the dimensions $must$ cancel

maheshmeghwal9 · Answer

so is 'a' right??

turingtest · Answer

right :)

maheshmeghwal9 · Answer

thanx a lot:D