Sometimes they are the same in physics. it depends how the question is worded but speed comes before velocity. If you take the derivative of speed you will end up with its velocity. The same goes when you take the integral of velocity.
        
                    
             
        
        
        
Option C: Later in the day, less power is developed in lifting each box
 
        
                    
             
        
        
        
Answer:
Choice a. 1 kg, assuming that all other forces on the object (if any) are balanced. 
Explanation:
By Newton's Second Law,
 ,
,
where
 is the acceleration of the object in is the acceleration of the object in , ,
 is the net force on the object in Newtons, and is the net force on the object in Newtons, and
 is the mass of the object in kilograms. is the mass of the object in kilograms.
As a result, 
 .
.
Assume that all other forces on this object are balanced. The net force on the object will be  . The net force is constant. Acceleration should also be constant and the same as the average acceleration in the two seconds.
. The net force is constant. Acceleration should also be constant and the same as the average acceleration in the two seconds. 
<h3>What is the 
average acceleration of this object?</h3>
 .
.
 .
.
<h3>Apply Newton's Second Law to find the mass of the object.</h3>
 .
.