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Below is the solution:
W done by Normal = 0. (make the incline flat, Normal force goes directly up: no work done) 
<span>W done by gravity = w*displacement = (11kg*9.8) * 7.5sin(35) = -463J </span>
<span>W done by friction is the opposite of the work done by weight because the object is not moving. Therefore W done by friction = 463J</span>
        
             
        
        
        
Answer:
a) k = 2231.40 N/m
b) v = 0.491 m/s
Explanation:
Let k be the spring force constant , x be the compression displacement of the spring and v be the speed of the box.
when the box encounters the spring, all the energy of the box is kinetic energy:
the energy relationship between the box and the spring is given by:
1/2(m)×(v^2) = 1/2(k)×(x^2)
     (m)×(v^2) = (k)×(x^2)
a) (m)×(v^2) = (k)×(x^2)
                  k = [(m)×(v^2)]/(x^2)
                  k = [(3)×((1.8)^2)]/((6.6×10^-2)^2)
                  k = 2231.40 N/m
Therefore, the force spring constant is 2231.40 N/m
b) (m)×(v^2) = (k)×(x^2)
              v^2 = [(k)(x^2)]/m 
                  v =  \sqrt{ [(k)(x^2)]/m}
                  v = \sqrt{ [(2231.40)((1.8×10^-2)^2)]/(3)}
                     = 0.491 m/s 
 
        
                    
             
        
        
        
Answer:
4541.8 J
Explanation:
First we find the mass of benzene available
mass = density x volume 
          = 0.867 x 34.1 
          = 29.5647 g
Then we find the amount of heat transferred by two processes:
heat tranferred = heat lost during temp drop + heat lost during freezing
                          = mcΔT + mL
                          = 29.5647 x 1.74 x (20.8 - 5.5) + 29.5647 x 127
                          = 4541.7883434 J
                          = 4541.8 J