Question

an object of 5 kg mass is placed on a cylindrical stand having circular cross section. the radius of the base of the stand is 4 cm. if the same object is placed on cylindrical stand with radius of the base of 8 and 2 cm the pressure becomes
1)One fourth 2)Half 3) Two times 4) Four times

Answer 1

Here first you have to define what is the contact area in between the two objects.

Case 1.
if the contact area is same in both of the cylinders then the pressure will not change and it will remain same in case of both of the cylinders.

Case 2.
Is the surface area of the object is more than the surface area of the smaller cylinder then when the object will be placed on larger cylinder the contact area will increase.

assuming that the contact area is same as that of surface area of the cylinder.

Pressure = (F/A)
A1 = πr² = 16π
A2 = πr² = 64π
A3 = πr² = 4π
(P1/P2) = (1/4)
(P1/P3) = (4/1)

so the new pressure will become 4 times of the initial pressure in case of 8 cm radius cylinder.

and it will become one fourth in case of 2 cm radius cylinder.

Answer 2

the answe is 1 as we know