circular motion physics help.. (1 Viewer)

[shantu1992]

heeey
how are youse?

need some help if thats alritee.

2. an object of 5g rotates at 4 revolutions per second around a circle of radius 15 cm. Calculate :

a) the linear speed ;
b) the centripetal acceleration

9. a mass of 1.6 kg moves in a circle of radius 22.0 cm at 3.00 revs/second, calculate;

a) the tangential velocity
b) centripetal acceleration; and
c) the centripetal forcee

thanks alot

 

[clintmyster]

I think the formula has been removed from the syllabus because I havent seen it yet but checking my textbook:

linear speed = (2 pi r ) x number of revolutions / T

centripetal acceleration = v²/r

2a) linear speed = (2pi x 0.15) x 4 / 1 = 3.77ms^-1

2b) centripetal acceleration = 3.77²/0.15 =94.75ms^-2

Im not 100% on part b tho. Itd be nice if you have answers?

 

[shantu1992]

thanks buddy i got similar answers to that aswell
ill find out the real ones real soon k

anyone elsee any help?

 

[I-Love-Jesus]

Well... I'll give it a go, but in no way am I confident of 2 (b) and 9 (b).

Sorry for all the dots =/

2) (a) velocity = distance/time
.................i.e v = 2*pi*r*number of revolutions/t
.........................= 2*pi*0.15*4/1
.........................= 1.2*pi
.........................~ 3.77 m.s^-1

.....(b) Centripetal force = mv²/r
.......................................F = ma
....................................ma = mv²/r
.......................................a = v²/r
.........................................,= (1.2*pi)²/0.15
..........................................~ 94.75 m.s^-2

I'm really not sure about part (b) as I just made up that connection, so I'm not sure whether centripetal acceleration = v²/r. Also, they have provided a mass, which appears to be of no use to us if that is the correct formula, leading me to believe it's not... Nonetheless, that is all I could come up with, so I'll do the same thing for 9) (b) as well.

9) (a) v = d/t
..............= 2*pi*r*number of revolutions
..............= 2*pi*0.22*3
..............= 1.32*pi
..............~ 4.15 m.s^-1
.....(b) a = v²/r
..............= (1.32*pi)²/0.22
..............~ 78.17 m.s^-2
.....(c) F = ma ..............................................or ................................................ F = mv²/r
..............~ 1.6*78.17 .......................................................................................... = 1.6*(1.32*pi)²/0.22
..............~ 125.07 N ........................................................................................... ~ 125.07 N

I hope that helps

 

[shantu1992]

thanks buddy