Answer:
1.52 m
Explanation:
We are given that
Maximum force=F=679 N
Mass of rock ,m=385 kg
Distance,d=0.233 m
We have to find the minimum total length L of the rod required to move the rock.
Torque on rock=
Where 
Torque on man=




Hence, the minimum total length of rod=1.52 m
Answer:
1) T = 4.5 s
2) T = 4.5 s
3) v = 9.9 m/s
Explanation:
We can use the equation
T = 2π√(L/g)
1) T = 2π√(5m/9.81 m/s²) = 4.5 s
2) T = 2π√(L/g)
T = 2π√(5m/9.81 m/s²) = 4.5 s
3) v = √(2gR)
v = √(2(9.81 m/s²)(5m))
v = 9.9 m/s