Question

A ball on the end of a string id spinning around a circle with a radius of 5 centimeters. If in 9 seconds a central angle of 1/3 radians has been covered, what is the angular speed of the ball?

Answer 1

As the ball is going 1/27 radians /s, all we need to do is go from that to angular speed.

Answer 2

The circumfrence of the circle is 10pi. Thus, the ball travels 10pi cm/2pi radians.

Answer 3

Multiplying the two cancels out the radians to give us cm/s, and so the answer is 5/27 cm /s or 0.19cm/s

Answer 4

can u tell me why the circumfrence is 10pi?

Answer 5

Circumference is 2pir. Radius is 5 cm, therefore the circumference is 2(5)pi or 10pi.

Answer 6

i still dont get it...how about this "9 seconds a central angle of 1/3 radians has been covered,"

Answer 7

In 9s, the ball has travelled 1/3 radians, right? If we divide both sides by 9, then that means that the ball has travelled 1/27 radians in 1 s.

Answer 8

oh ok gotcha...just let me double check this :)

Answer 9

i got another :)
A bicyclist average linear speed during a race was 36 mph. His bicycle wheel has a 20-in diameter. What was the angular speed of the wheel in revolutions per hour?

Answer 10

Damn americans and their imperial system... lol jk one sec.

Answer 11

63360 inches in a mile? What sort of messed up system is that?

Answer 12

Okay fine so the bicycler traveled 2 280 960 inches per hour. The wheel rotated 20pi inches each revolution. Therefore, the number of revolutions per hour would be 2 280 960 divided by 20pi, or around 36 302.6

Answer 13

Man, I am GLAD I don't live down there. One unit in Grade 9 for the Imperial System was enough for me.

Answer 14

man...is this real? jk

Answer 15

what do u mean down there? where do u live?

Answer 16

I'm Canadian.

Answer 17

lol

Answer 18

a wheel with 21 inch diameter is turning at the rate 43 revolutions per minute. To the nearest inch per minute, what is the velocity of a point on the rim?

Answer 19

@greenglasses

Answer 20

Bloody inches.

Answer 21

It's the same basic concept as the other questions. The wheel's got a radius of 21pi right? So that means it travels 43 (21pi)/min.

Answer 22

*diameter

Answer 23

No wait.

Answer 24

linear velocity?

Answer 25

dude...we got diameter so we got radius
then 43 revolutions => w= 43x2 pi

Answer 26

velocity is linear speed lol

Answer 27

Sorry what's w?

Answer 28

angular speed

Answer 29

what do u think man?

Answer 30

my mind's bust I'm tired of physics. i googled it the answer is definitely c). the answer is always c). also 43 x 2 x pi is not one of the answers.

Answer 31

http://bethanyshultz.weebly.com/uploads/2/2/6/1/22614328/linearspeed.pdf

Answer 32

lol the angular speed = revolutions x 2pi if u have revolutions
the linear speed = r x angular speed
by this i solve the second problem that i gave u, and the answer is 36302.6059 revs lol

Answer 33

this is not physics man...im working on trig lol