A)	work = force * distance 
mass is not a force, weight is, so we have to find the weight of the block. 
Weight = mg 
Weight = (220kg)(9.8) 
Weight = 2156N 
Work = 2156N * 3.10m 
work = 6683.6J 
b)	Since he is holding the weights, it's not moving, therefore, he doesn't do any work 
c)	The answer is still the same amount of work when he lifted them. 
d)	The answer is no since when he let go the weight, he doesn't apply any force to the weight. 
e) P = work/time 
P = 6683.6J / 2.1s 
P = 3182.67 watts 
        
             
        
        
        
It is either a person who studies Linguistics or 
a person skilled in foreign languages 
 
        
             
        
        
        
Here is your answer 

REASON : 
We know that
Potential difference, V= W/q
where, W is work done
and, q is magnitude of charge
Given,
V= 9.0 v and W= 45 J
So,
using above relation, we get 
9= 45/q
q= 45/9
q= 5 coulomb 
HOPE IT IS USEFUL 
 
        
             
        
        
        
Answer:
The length of the closed tube is<u> </u>
<u>0.81 m</u>
Explanation:
Formula used :

 
 
 Speed = v = 346 m/s

 
 

wavelength = 0.81 m