Answer:
Solon, 
total mass (kg)= 100kg
height (h)= 25m
acceleration due to gravity = 9.8m/s²
so, 
work done =m*g*h
 = 100*9.8*25
= 24,500 joule
 
        
             
        
        
        
Question: How fast was the arrow moving before it joined the block?
Answer:
The arrow was moving at 15.9 m/s. 
Explanation:
The law of conservation of energy says that the kinetic energy of the arrow must be converted into the potential energy of the block and arrow after it they join:

where  is the mass of the arrow,
 is the mass of the arrow,  is the mass of the block,
 is the mass of the block,  of the change in height of the block after the collision, and
 of the change in height of the block after the collision, and  is the velocity of the arrow before it hit the block.
 is the velocity of the arrow before it hit the block.
Solving for the velocity  , we get:
, we get: 

and we put in the numerical values
 ,
,



and simplify to get: 

The arrow was moving at 15.9 m/s
 
        
             
        
        
        
Thomas Edison is the answer im 100% sure of it.
        
             
        
        
        
Answer:
500 m
Explanation:
t = Time taken
u = Initial velocity = 50 m/s
v = Final velocity = 0
s = Displacement
a = Acceleration = -2.5 m/s²
Equation of motion

Time taken by the train to stop is 20 seconds

∴ The engineer applied the brakes 500 m from the station