Seriously? It’s that hard to use a calculator??
 
        
             
        
        
        
Answer:
21.21 m/s
Explanation:
Let KE₁ represent the initial kinetic energy.
Let v₁ represent the initial velocity. 
Let KE₂ represent the final kinetic energy. 
Let v₂ represent the final velocity.
Next, the data obtained from the question:
Initial velocity (v₁) = 15 m/s
Initial kinetic Energy (KE₁) = E
Final final energy (KE₂) = double the initial kinetic energy = 2E
Final velocity (v₂) =? 
Thus, the velocity (v₂) with which the car we travel in order to double it's kinetic energy can be obtained as follow:
KE = ½mv²
NOTE: Mass (m) = constant (since we are considering the same car) 
KE₁/v₁² = KE₂/v₂²
E /15² = 2E/v₂²
E/225 = 2E/v₂²
Cross multiply 
E × v₂² = 225 × 2E
E × v₂² = 450E
Divide both side by E
v₂² = 450E /E
v₂² = 450
Take the square root of both side. 
v₂ = √450
v₂ = 21.21 m/s
Therefore, the car will travel at 21.21 m/s in order to double it's kinetic energy. 
 
        
             
        
        
        
Answer:
 T = 188.5 s, correct is  C
Explanation:
This problem must be worked on using conservation of angular momentum. We define the system as formed by the fan and the paper, as the system is isolated, the moment is conserved
          
initial instant. Before the crash
         L₀ = r m v₀ + I₀ w₀
the angular speed of the fan is zero w₀ = 0
final instant. After the crash
         L_f = I₀ w + m r v
         L₀ = L_f
         m r v₀ = I₀ w + m r v
angular and linear velocity are related
         v = r w
         w = v / r
         m r v₀ = I₀ v / r + m r v
          m r v₀ = (I₀ / r + mr) v
        v = 
let's calculate
        v = 
        v = 
        v = 0.02 m / s
          
To calculate the time of a complete revolution we can use the kinematics relations of uniform motion
         v = x / T
          T = x / v
the distance of a circle with radius r = 0.6 m
          x = 2π r
we substitute
          T = 2π r / v
let's calculate
          T = 2π 0.6/0.02
          T = 188.5 s
reduce
          t = 188.5 s ( 1 min/60 s) = 3.13 min
 correct is  C
 
        
             
        
        
        
Explanation:
It is given that,
Displacement of the delivery truck,  (due east)
 (due east)
Then the truck moves,  (due south)
 (due south)
Let d is the magnitude of the truck’s displacement from the warehouse. The net displacement is given by :


d = 4.03 km
Let  is the direction of the truck’s displacement from the warehouse from south of east.
 is the direction of the truck’s displacement from the warehouse from south of east.


So, the magnitude and direction of the truck’s displacement from the warehouse is 4.03 km, 37.4° south of east.