mechanics help! (1 Viewer)

fahadmumtaz88

wasim akram
Joined
Oct 2, 2004
Messages
23
Location
liverpool
Gender
Male
HSC
2005
I tried this question but the answer in the back seems to be different, can someone help me out? thanks

The questions are:

1) If a conical pendulum is 1.4m long and the semivertex angle of the cone is 30 degrees find the period of rotation adn the tension in the string when the mass of the particle is 10 kg.



2) An inextensible string of length 2m is fixed at one end and carries at its other end B a particle of mass 6 kg which is rotating in a horizontal circle whose centre is 1m vertically below A. Find the tension in the string and the angular velocity of the particle.
 

KFunk

Psychic refugee
Joined
Sep 19, 2004
Messages
3,323
Location
Sydney
Gender
Male
HSC
2005
fahadmumtaz88 said:
The questions are:

1) If a conical pendulum is 1.4m long and the semivertex angle of the cone is 30 degrees find the period of rotation adn the tension in the string when the mass of the particle is 10 kg.
Let the tension in the string be T.

∑ vertical forces = 0 ,

i.e. Tcos30° = mg ,
T = mg/cos30° = 200/√3 N

*note: this is the same as 20 √3/3 kg wt ... fitz notation is retarded

&sum; horizontal = mw<sup>2</sup>r

Tsin30&deg; = mw<sup>2</sup>r
w = &radic;[Tsin30&deg;/mr] where r = 0.7m

then T = 2&pi;/w which is 2. something seconds
 

KFunk

Psychic refugee
Joined
Sep 19, 2004
Messages
3,323
Location
Sydney
Gender
Male
HSC
2005
fahadmumtaz88 said:
2) An inextensible string of length 2m is fixed at one end and carries at its other end B a particle of mass 6 kg which is rotating in a horizontal circle whose centre is 1m vertically below A. Find the tension in the string and the angular velocity of the particle.
Let the tension in the string be T and note that the lengths given create that basic triangle with angles 30, 60 and 90&deg;

&sum; vertical = 0 so Tcos60&deg; = mg
T = 2mg (1)

&sum; horizontal = mrw<sup>2</sup>

Tsin60&deg; = mrw<sup>2</sup>

mg&radic;3 = mrw<sup>2</sup> from (1) &there4; w = &radic;(&radic;3g/r)

[put the values in to get your numerical answer. I'm not sure what values of g you're using]
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top