Question

your car tire is rotating at 3.5 rev/s, when suddenly you press hard on the accelerator. after traveling 200 m, the tire's rotation has increased to to 6.0 rev/s. what was the tires angular acceleration?

Answer 1

You should probably stick this in physics, but

Answer 2

what is the formula for angular accel?

Answer 3

dw/dt

Answer 4

the problem is finding dt without the radius.

Answer 5

and how do you calculate d(omega)?

Answer 6

its 5pi but I can't figure out how long the process takes.

Answer 7

all it wants is the accel though?>

Answer 8

dw is not the acceleration, to find acceleration you need to know how long the change in omega took

Answer 9

omega is ang velocity no? and average ang accel has multiple ways to calculate right? Assuming constant accel and given dw, and s

Answer 10

dw=?

Answer 11

ds/dt no?

Answer 12

use that to calculate dt

Answer 13

correct but ds is a function of r, which unknown

Answer 14

use the formula w^2-w_0^2=2 alpha theta

where w is the final angular velocity, and w_0 is the initial angular velocity. Alpha is the angular acceleration and theta is the angular displacement.


I am not sure ........will this work????.....:(

Answer 15

ds = 200m. which makes d(theta) = 200/r
and praxar that looked promising but I still end up with alpha*theta, neither of which I know. I need r to find theta

Answer 16

we will find the alpha so there is no need to have it I think so...:O

Answer 17

Ya but we need to get the radius... first...:)

Answer 18

how do we get the radius?

Answer 19

hmmm

Answer 20

@Dom89 Please check the question once again.. I think the radius must be given else it is just impossible to get hook of the solution..... i think so.......

Answer 21

k try these, \(d\theta={d\omega}{dt}\)and

Answer 22

http://openstudy.com/study#/updates/51c57ae5e4b069eb00c573b6

Similar question but here the radius is given....

Answer 23

\[\omega_f=\omega_i+2\alpha t\]
and
\[d\theta=\omega_i t+ .5 \alpha t^2\]

Answer 24

3 variables, 3 eq

Answer 25

don't you need one more equation than you have unknowns to find the unknowns?

Answer 26

note \[\frac{d\theta}{dt}=d\omega\]

Answer 27

no, just the same amount

Answer 28

otherwise it's redundant

Answer 29

and not LI

Answer 30

sorry for the abrupt stop i got called to work. @praxer I checked the question, it definitely does not give the radius.

Answer 31

thanks for the help guys but I asked a few people at uni and they all agreed it must be a mistake in the question. It's unsolvable without more info.

Answer 32

Ok, that makes sense, otherwise you have a serious system of eq to solve haha