Question

5.
A meter scale of mass 400 gm is lying
horizontally on the floor. If it is to be held
vertically with one end touching the floor, the
work to be done is
1) 6J 2) 4J 3) 40J4) 2 J​

Answer 1

Answer:

The answer si 2J.

Explanation:

Initially, the scale is lying on zero potential lines, therefore the initial potential is  

Ui = 0

Mass of the meter = 400 g

Now divide with 1000 to convert into Kg.

Mass of the meter = 400 /1000 = 0.4 Kg

Center of the mass of the scale lies at its center i.e.  

h = 0.5 m

The final potential energy of the scale = Uf = mgh

                                                             = 0.4 x 10 x 0.5 = 2J

Hence work done = Uf - Ui = 2J - 0 = 2J