Daniel B. answered 01/24/21
A retired computer professional to teach math, physics
1)
a) There are two forces:
T: as drawn
G: gravity due to the mass M of the pulley
b)
Moment of T is TR
Moment of G is 0, because the pulley center of gravity is also the center of rotation.
c)
TR = Iθ"
T = Iθ"/R = MR²θ"/2R = MRθ"/2
2)
a) There are two forces:
T' as drawn upward
G: force of gravity downward
b)
G - T' = ma
T' = G - ma
3)
T = T' by Newton's Third Law
MRθ"/2 = mg - ma
Ma/2 = mg - ma
a = mg/(M/2 + m)
Substituting actual values:
a = 1kg × 10m/s² / (3kg + 1kg) = 2.5m/s²