Answer:
Zero
Explanation:
As force acting on the body is equal to the product of mass and acceleration. 
Acceleration is equal to rate of change in velocity.
Here velocity is constant so acceleration is zero. 
It means the net force acting on the vehicle is zero.
 
        
                    
             
        
        
        
Answer:
Work done to pull the piano upwards is 401250 J
Explanation:
Work is done against the gravity to pull the piano upwards
So here we can say that work done is 

here we know that

also we know that
H = 75 m
now we have


 
        
             
        
        
        
Answer:
5760 J
Explanation:
From the question given above, the following data were obtained:
Mass of block = 48 kg
Height (h) = 12 m
Gravitational field strength (g) = 10 N/Kg
Gravitational potential energy (PE) =? 
The gravitational potential energy stored by the block can simply be obtained as follow:
PE = mgh 
PE = 48 × 10 × 12
PE = 5760 J
Therefore, the gravitational potential energy stored by the block is 5760 J