# What must be the tangential speed of the puck so that the hanging cylinder remains motionless? Calculate revolution per second.?

A puck of mass m = 1.50 kg slides in a circle of radius r = 22.0 cm on a frictionless table while attached to a hanging cylinder of mass M = 3.15 kg by a cord through a hole in the centre of the table. Ignore the mass of the cord and you may ignore any friction of the cord through the hole.

(a) What must be the tangential speed of the puck so that the hanging cylinder remains motionless?

(b) How many revolutions per second does the puck make?

### 1 Answer

- 2 years agoFavorite Answer
a)

m1 = 1.50 kg

r = 0.22 m

m2 = 3.15 kg

(v)t = wr

(m2)g = [(m1)v^2]/r

v = square root [(r*m-2*g)/m-1]

Plug in values and you get 2.13 m/s.

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b) (v)t = rw

w = v/r = (2.13)/(0.22) = 9.67 rad/s

rad --> rpm

w = 9.67 rad/s * 60s/1 min * 1 rev/2pi rad = 92.36 rpm