Answer: The angle between force and displacement should be θ = 90° for minimum work. The angle between force and displacement should be θ = 0° for maximum work.
Water? The sun. I DUNNO I FEEL BAD :(
A) 
Let's start by writing the equation of the forces along the directions parallel and perpendicular to the incline:
Parallel:
(1)
where
m is the mass
g = 9.8 m/s^2 the acceleration of gravity
is the coefficient of friction
R is the normal reaction
a is the acceleration
Perpendicular:
(2)
From (2) we find
And substituting into (1)
Solving for a,
B) 5.94 m/s
We can solve this part by using the suvat equation
where
v is the final velocity
u is the initial velocity
a is the acceleration
s is the displacement
Here we have
v = ?
u = 0 (it starts from rest)
s = 8.70 m
Solving for v,
Answer:
Minimum elastic modulus of fiber = 455.64 GPa
Explanation:
Contents of composite material = Epoxy and Unidirectional fibers
Elastic modulus of epoxy = 3.5 GPa
Elastic modulus of composite material = 320 GPa
Volume fraction of fiber = 70 %
Volume fraction of epoxy = 100 - 70 = 30%
Elastic modulus of composite material = 3.5 x 0.3 + Elastic modulus of fiber x 0.7 = 320
0.7 x Elastic modulus of fiber = 320 - 1.05 = 318.95
Elastic modulus of fiber = 455.64 GPa
Minimum elastic modulus of fiber = 455.64 GPa
