DaddyFed is right, it would be all of them.
        
             
        
        
        
Answer:
a) a = 2.383 m / s², b)   T₂ = 120,617 N
, c)   T₃ = 72,957 N
Explanation:
This is an exercise of Newton's second law let's fix a horizontal frame of reference
in this case the mass of the sleds is 30, 20 10 kg from the last to the first, in the first the horizontal force is applied.
a) request the acceleration of the system
we can take the sledges together and write Newton's second law
      T = (m₁ + m₂ + m₃) a
     a = T / (m₁ + m₂ + m₃)
      a = 143 / (10 +20 +30)
      a = 2.383 m / s²
b) the tension of the cables we think through cable A between the sledges of 1 and 20 kg
on the sled of m₁ = 10 kg
           T - T₂ = m₁ a
in this case T₂ is the cable tension
            T₂ = T - m₁ a
             T₂ = 143 - 10 2,383
             T₂ = 120,617 N
c) The cable tension between the masses of 20 and 30 kg
             T₂ - T₃ = m₂ a
              T₃ = T₂ -m₂ a
              T₃ = 120,617 - 20 2,383
              T₃ = 72,957 N
 
        
             
        
        
        
Answer:
36,67 degrees Celsius
Explanation:
The simplest way to approach this problem, given the information provided, is to simply start with the speed difference.
Goal: 353 m/s
Start: 343 m/s (at 20 degrees Celsius).
Difference: 10 m/s
Variation rate: 0.60 m/s/d (d = degree)

So, 16,67 degrees more than the starting point.
The temperature will then be 36.67 degrees Celsius, when the sound travels at the speed of 353 m/s.
 
        
             
        
        
        
It rises till all of its Kinetic energy is converted into potential energy.
so, mgh=(1/2)m(v^2)
so, h=(v^2)/2g = 12*12/(2*9.81)=7.34 m
        
             
        
        
        
Answer: is A
The acceleration of an object is determined by its mass and the net force acting on it.
Newton's second law says that "F=ma". what this means is that the force you apply to an object is equal to its mass times how fast it is accelerating.
Hope it helped.