Question

find the work done in lifting a stone of mass 10kg and specific gravity 3 from the bed of a lake to a height of 6m in water

Answer 1

Hey friend,
Here is the answer you were looking for:
As we all know the formula of potential energy is= m×g×h
And potential energy comes under work done.
So, Here;
It is given that,
Mass= 10kg
Gravity= 3 nm^2/kg^2 from bed
And, Height= 6m
So,
Work done = m×g×h
=10×3×6
=180 joules
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Answer 2

Answer:

Apparent weight =mg−F  

B

​

 

where, F  

B

​

 is buoyant force and mg is weight

We know that buoyant force F  

B

​

 will be:

F  

B

​

=Vρ  

water

​

g=  

ρ  

stone

​

 

m

​

ρ  

water

​

g

where V is volume of stone =  

ρ  

stone

​

 

m

​

 and  ρ  

water

​

 is density of water

As specific gravity is given as 3 it's density will be three times of water

ρ  

water

​

 

ρ  

stone

​

 

​

=3

Hence, F  

B

​

=  

3

mg

​

 

Putting the values of m,g and applying the formula for work done,

Work done = Apparent weight × displacement

                   =10×g×h−  

3

10×g

​

×h

                   =  

3

2

​

×10×10×6

                   =400 J

Explanation: