Question

there is a useful grass and weed cutting tool that utilizes a 0.21-m length of nylon "string" rotating at 6200 rev/min about an axis perpendicular to one end of the string. (a) What is the time needed for the string to sweep out an angle of 35 degree? (b) Assuming that the length of the string does not change, find the distance through which the tip of the string moves during this interval.

Answer 1

6200 rev/min = frequency of rotation
do you know formula for angular velocity ω ?

Answer 2

ω = θ / t

Answer 3

wright!
but that is the definition of ω
you will use it after you have calculate the ω
now formula for ω involving frequency???

Answer 4

I don't know.

Answer 5

ω=2 π f

Answer 6

note
you have to convert rev/min to rev/sec

Answer 7

Alright.

Answer 8

so we have
ω=2*π* f
ω=θ/t
there for 2*π*f=θ/t
t=θ/2πf
f to rev/sec and θ to rad

Answer 9

Thanks let's see if I can solve it now.

Answer 10

you should find t=9.4086exp-4 sec

Answer 11

This is what I got for the first equation
6200 rev/min = 103.3 rev/s
ω = 2π(103.3)
ω=648.724

Answer 12

Am I correct ?

Answer 13

what you use for π ?

Answer 14

pi= 3.14

Answer 15

ok you are correct

Answer 16

how ever you could have a more acurate resalt if
t=θ/2πf
θ=(35/360)*2π rad
f=6200/60 Hz
t=....... t=(35*2π*60)/360*2π*6200
...t=9.4086exp-4 sec
this way you use your calculator only once at the end and have only one aproximation

Answer 17

in my place of the planet that is the way we do calculations
don;t know if that is axeptable for you...

Answer 18

My teacher didn't teach me that way

Answer 19

ok folow you way

This is what I got for the first equation
6200 rev/min = 103.3 rev/s
ω = 2π(103.3)
ω=648.724 rad/sec

so far OK

Answer 20

now you have to convert degrees to rad
do you know how?

Answer 21

35 degree = 0.6108652381965 rad

Answer 22

0.61055555555555555555rad

Answer 23

in your calculator:
35
/
360
=
*
2
*
3.14
=
0.61055555555

Answer 24

now you have
θ=0.610555 rad
ω=648.724 rad/sec
go for t

Answer 25

Alright thanks

Answer 26

I got 1062.5

Answer 27

for your next question