# Which of the following is vector and which is scalat

1. Mar 25, 2012

### vkash

which of the following is vector and which is scalar?????

angular velocity and angular acceleration are __________ quantity..
my answer is vector. am i correct.
here i am considered about only rotational motion.
somewhere in book it is written as non vector. that's why i am asking it.

Last edited: Mar 25, 2012
2. Mar 25, 2012

### vkash

Mod node:

a car is moving in x direction of reference frame with a velocity of 50ms-1. IS it vector or scalar...? i think that's vector.

this is question in my last FIITJEE test. in that test it was question in matrix match, in one side there were these two quantities and in other side their was an option of vector quantity.,

In exam it has never been mentioned that either a thing is vector or scalar. but i always assume that it is vector to approach my question..

i don't know <><><>
i think this might be because of these formulas. L=Iω , L[angular momentum] is vector I[moment of inertia] is not a vector so w[angular velocity] must have been a vector quantity.. IT seems like foolish answer but i am not getting any other answer for this.

Last edited by a moderator: Mar 28, 2012
3. Mar 25, 2012

### cepheid

Staff Emeritus
You are making this way too complicated. Just look up the *definitions* of these two quantities to see if they are vector or scalar.

4. Mar 25, 2012

### vkash

http://en.wikipedia.org/wiki/Angular_velocity
They mention it in 1st line. It is a vector quantity. similarly it's derivative with respect to time will also a vector.

5. Mar 26, 2012

### D H

Staff Emeritus
The answer is "it depends". In particular, it depends on the dimensionality of the space and whether one considers pseudovectors to be vectors.

In the context of rotations in three dimensional space, angular velocity and angular acceleration can be treated as vectors. Angular velocities and accelerations in ℝ3 have an additive inverse, add, and can be multiplied by a scalar. In this sense they are vectors. They do not act like position and velocity vectors upon reflection. In this sense they are pseudovectors. However, pseudovectors are vectors if you look at them from the context of being a member of a vector space.

Angular velocity and angular acceleration in any dimensional space other than ℝ3 are not vectors. They are instead bivectors or 2-forms. However, this FIITJEE test is apparently with regard to engineering problems. Engineers worry primarily about problems in our 3D world, where angular velocity and angular acceleration are vectors.

Without further details about the question at hand, I would agree that you have the correct answer, vkash.