Question

14. A uniform metre scale of mass 50 g is balanced on the edge of a knife at mark 60 cm by suspending an unknown mass at the 80 cm
mark. Find the value of the unknown mass​

Answer 1

Answer:

Explanation:

Since, uniform metre rule of mass 100 g is balanced on a fulcrum at mark 40 cm.

so, distance of c.o.m. of rule from balanced point is 10cm.

Net moment at balancing point should be zero.

So, m×20 = 100×10 m = 50g

if m is moved to mark of 10cm then rule will tilt to the side where m is suspended.

Now, for balance this

50×30 = 100×10+ 50×(x-40) (x-40) = (1500- 1000)/50 = 10cm X = 50cm.

So, another 50g mass will be suspended at 50cm mark

Answer 2

Answer:

The value of unknown mass is 25g.

Explanation:

Given,

• The mass balanced at the edge of the scale = 50 g
• Mass balanced on the edge of knife is marked by 60 cm
• The unknown mass was marked at 80 cm

To find:

• The value of unknown mass.

Solution:

The moment of force are equal and the mass balance each other.

The distance between the mass at two point = 60 cm - 80 cm

                                                                           = - 20 cm

Mass balance at one side = m(60-80)    ......................(1)

Mass balance at other side = 50(50-60)   ...................(2)

Balance equation(1) and equation(2)

m(60 cm-80 cm) = 50(50 cm -60 cm)

Note: 50 cm is the center distance

m (-20) = 50 (-10)

-20 m = -500

m = 25 g     ............................(3)

Therefore, The value of unknown mass is 25g.

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