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Peach Peach
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11 years ago
1-a mass m1=2 kg undergoes a circular motion of radius R on a horizontal frictionless table. the mass m1 is connected to a second mass m2=3 kg through a smooth hole in the table. when R=0.5m, the mass m2 is stationary, what is the period of the mass? (T= square root of 4 pie^2R/ ac, where ac is the centripetal acceleration of m1)

2- two blocks having masses m ans 3m connected by a massless string thar passes over a frictionless pulley. the 3m block is on a horizontal frictionless table, the other is hanging. the magnitude of the acceleration of the system of masses is?

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Valued Member
On Hiatus
11 years ago
1) See picture at attachment.
Mass 2 is stationary, so ΣF of mass 2=0. So, T1=W <=> T1=3*g
T2=T1 because T2 is the reaction of T1
T3=T2 (otherwise the rope would break)
T4=T3=3*g because T4 is the reaction of T3.

T4 is the centripetal force.
So, the centripetal acceleration should be: T4/m2=(3/2)*g and if we assume that g=9,8:
ac=14,7m/s2

And using the formula, we have:
T=square root of: (4π2*R/ac)=square root of: [4,935/14,7]=0,58 seconds

2)
We have: the acceleration of mass m is the same as the acceleration of the mass 3m (the rope is inextensible and not loose)
In addition, T1=T4 (for the same reason as the previous exercise)
The acceleration of mass m is: (W-T1)/m
The acceleration of  mass 3m is: T4/3m
So, we have (W-T1)/m=T4/3m <=> 3*(m*g-T1)=T4 <=> 3*m*g-3T1=T1 <=> 4T1=3*m*g <=> T1=(3/4)*m*g.

We already said that a=T4/3m (or a=(W-T1)/m , you can use whichever equation you want)
So: a=T4/3m <=> a=T1/3m <=> a=[(3/4)*m*g]/3m <=> a=(1/4)*g or a=2,45m/s2 if we assume that g=9,8m/s2.

(See attachment for pictures for both exercises)
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