Given :
A 120 kg box is on the verge of slipping down an inclined plane with an angle of inclination of 47º.
To Find :
The coefficient of static friction between the box and the plane.
Solution :
Vertical component of force :

Horizontal component of force(Normal reaction) :

Since, box is on the verge of slipping :

Therefore, the coefficient of static friction between the box and the plane is 1.07.
Hence, this is the required solution.
A. cleaning up after environmental disasters
Answer:
a. 3 s.
Explanation:
Given;
angular acceleration of the wheel, α = 4 rad/s²
time of wheel rotation, t = 4 s
angle of rotation, θ = 80 radians
Apply the kinematic equation below,

Given initial angular velocity, ω₀ = 0
Apply the kinematic equation below;

Therefore, the wheel had been in motion for 3 seconds.
a. 3 s.
B. Tornado destruction
It is based on the amount of damage