Question

Medal award!
Can someone help me?
If this circle (disc) spins 20 revolutions per minute, what is the angular speed?

what would the linear speed be at point p in m/s?

Answer 1

2.1 = angular speed.

Answer 2

37.7 linear speed.

Answer 3

how do you set it up?

Answer 4

well for linear speed, it is [circumference times 20] divided by 60

Answer 5

so, wait soryr. i calcualted wrong units.

Answer 6

it'd be 10.47 for linear speed.

Answer 7

and angular speed is linear speed/r is one formula for angular speed.

Answer 8

i'm not sure how to figure out the circumference :/

Answer 9

angular speed = 2pi(frequency) = 2pi / (period) = linear speed / radius.

Answer 10

area of circle is (pi)r^2. circumference is 2pi(r).

Answer 11

wait, sorry, legit confused here, why are they teaching you revolutions and such without teaching how to find circumference/

Answer 12

no i'm just confused about how the circumference is applied here..

Answer 13

because all that is know is the radius and the 40 degrees

Answer 14

well, think of it like a wheel rolling. if a wheel rolls 20 times, how would you figure out how far it has rolled? Well, the way to think about it is, what if you took a belt, and made it into a circle with radius 5? now, straigten the belt. now take 20 belt lengths. that's what i'm doing here.

Answer 15

if a wheel rolls once, the distance it covers on the ground is 1 circumference. get it?

Answer 16

oh ok :) thanks

Answer 17

in terms of figuring out the angular and linear speeds how would I apply this rule?

Answer 18

well for linear speed, it's the same as finding speed of a car. total distance divided by total time. so 20 revoltuions divided by 60 seconds.

Answer 19

and if you scroll up, you'll see teh three equations i posted that you can use to find angular speed.

Answer 20

oh ok thanks so much I just got confused because when I divided 20/60 I got .333 repeating and not 10.47

Answer 21

glad you figured it out.