Answer:
the coefficients of static friction is 0.577
the coefficients of fkinetic friction is 0.54
Step-by-step explanation:
given information
θ = 30°
S = 2.5 m
t = 4 s
- Static friction
F - F(friction) = 0
W sin θ = μs W cos θ
μs = sin θ/ cosθ
= tan θ
= tan 30°
= 0.577
- kinetic friction
S =
+ 
= 0
S = 
a =
= 
= 0.3 
F - F(friction) = m a
W sin θ - μ W cos θ = m a
mg sin θ - μk mg cos θ = m a
g sin θ - μk g cos θ = a
μk = g sin θ - a / g cos θ
= 9.8 sin 30° - 0.3 / 9.8 cos 30°
= 0.54
The side length has to be between 2 (=9-7) and 16 (=9+7). In both these corner cases the triangle will have collapsed to a line.
So the correct answers are B,C,D and E, and F is a corner case. Theoretically I suppose you have to count F in as a valid answer.