A 0.420 kg pendulum bobpasses through the lowest part of its path at a speedof 3
ID: 1743606 • Letter: A
Question
A 0.420 kg pendulum bobpasses through the lowest part of its path at a speedof 3.70 m/s. (a) What is the tension in the pendulum cable at this point if thependulum is 80.0 cm long?N
(b) When the pendulum reaches its highest point, what angle doesthe cable make with the vertical?
°
(c) What is the tension in the pendulum cable when the pendulumreaches its highest point?
N (a) What is the tension in the pendulum cable at this point if thependulum is 80.0 cm long?
N
(b) When the pendulum reaches its highest point, what angle doesthe cable make with the vertical?
°
(c) What is the tension in the pendulum cable when the pendulumreaches its highest point?
N
Explanation / Answer
a.) T - mg = mv^2/r, where v = velocity of the boband r = cable length.=> T
= m(g + v^2/r)
= (0.42)[9.8 + ((3.7)^2/0.8)]
= 11.3 N
b.)
(2r)*sin^2(/2) = v^2/2g
sin(/2) = v / 2(rg)
sin(/2) = 3.7 / 2(0.8)(9.8)
sin(/2) = 0.6607
= 82.705°
c.) At the highest point, its velocity is zero. So no centripetalforce on it. Hence, T should equal the component of mg in itsdirection.
T = mg cos 82.706° = (0.42)(9.8) (0.127)
T = 0.5227 N
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