Question

A truck is moving at a rate of 105 kilometers per hour, and the diameter of its wheels is 1 meter. Find the angular speed of the wheels in radians per minute.

Answer 1

w=theta/r

Answer 2

Ok, so this is confusing to me because I don't know where to start. I don't know how many revoluitions.

Answer 3

find V in m/s
r=1/2
V=r*omega => omega =V/r

Answer 4

hmm. sorry, I don't think we use that formula.

Answer 5

I mean the omega part...

Answer 6

omega is angular velocity.

Answer 7

Angular speed =theta/t

Answer 8

yes

Answer 9

OK we use angular speed=theta/time

Answer 10

k.

Answer 11

do I have to convert the kilometers to miles?

Answer 12

also remember once you find omega to convert from rad.s / sec to rad.s /min , since that's the units they want (for no apparent reason)

Answer 13

meters / second or meters/ minute, I guess.

Answer 14

well...on the omega...we haven't used that term. So I don't know how to do that.

Answer 15

Here's an example of what I think I am supposed to do.

Answer 16

The blades of a wind turbine are 116 feet long. The propeller rotates at 15 revolutions per min.

Answer 17

Maybe that's a bad example.

Answer 18

there's nothing to do.
just like 'x' is distance and x/t is velocity (for unaccelerated motion)
"theta" is 'angular distance' and theta/t is angular velocity

Answer 19

a. Because each relvoltion generates 2pi radians, it follows that the propeller turns (15)(2pi)=30pi radians per min. The angular speeds is

Answer 20

Angular speed =theta/r

Answer 21

30pi radians/1 min=30 radians per min

Answer 22

I don't want to sound like a typical cry baby in math..but the work give one example then the homework is similar but....it's a vague book.

Answer 23

So, given that's the only example in the section...IDK.

Answer 24

that example you gave is just converting rev.s to rads.

Answer 25

exactly....I will see if there's something like it in a different...sect.

Answer 26

nm.

Answer 27

Well, that's just a question at the end of the chap....just case something shows up like it on the exam. We didn't do a prob. like that so I better move on...we did do plenty of other problems to work on.

Answer 28

here:


(2pi radians) *1/2 m = circumference (one rev)

so:
find V in meters/min
r*theta/min = V

Answer 29

But, I don't know theta.

Answer 30

you know V and r

Answer 31

theta/min = V/r

Answer 32

you're over thinking this... if a rolling wheel makes one complete rev (2pi radians),
it has traveled forward a distance of 2pi*r
two rev.s -> 4pi*r etc
so whatever distance it travels forward = theta*r
in a minute this wheel travels 1750m
so theta*r =1750
theta = 3500 rad.s

aka V/r

Answer 33

ah....that's easier...

Answer 34

I guess I don't understand how to find theta.

Answer 35

think about a string wrapped around the rim of a tire. the string is as long as the circumference. roll the tire forward one complete rev. the string unrolls completely: the tire has traveled forward one circumference = 2pi*r

Answer 36

it's 3500 rad.s

every minute.

Answer 37

k, good on this? is it clearer? or questions?

Answer 38

I think am I ok...It's a lot to cram in my simple brain. lol. I am trying...:)

Answer 39

what are you studying anyway?

Answer 40

some physics+math class without calculus?

Answer 41

or two different classes?

Answer 42

trig and Microbiology