Question

a rectangular wooden block has l,h,b as 50cm,25cm and 10cm respectively.find the magnitude of pressure in all cases where the wooden block is kept on ground in 3 different ways

Answer 1

> Let the force be F

Air on which force is applied can be of three types
(i) When l = 50cm & b = 10cm
» A = 0.5m × 0.1m = 0.05m²

(ii) When l = 10cm & b = 25cm
» A = 0.1m × 0.25m = 0.025m²

(iii) When l = 25cm & b = 50cm
» A = 0.5m × 0.25m = 0.125m²

When force is applied on 1st surface
= F/0.05 = 100F/5 = 20F

When force is applied on 2nd surface
= F/0.025 = 1000F/25 = 40F

When force is applied on 3rd surface
= F/0.125 = 1000F/125 = 8F

Therefore, Pressure can be applied in three ways with 20F, 40F & 8F pascals

Answer 2

Pressure = Force exerted on an area / Area
P = F / A

Let the Weight of the wooden block be W dynes.

Rectangular wooden block :  l = 50 cm,  b = 25 cm,  h = 10 cm

Wooden block is kept on the face with dimensions = 

   1) l X b = 50 cm X 25 cm
  
            P = W / 1,250  dynes/cm²

   2)  b X h = 25 cm * 10 cm

           P = W /250 dynes/cm²

  3)  l X h = 50 * 10 cm

        P = W /500 dyne/cm²

The ratio of pressures when it is kept on the ground in three different ways :

       W/1250 :  W/250  : W /500
   =   1 : 5 : 2.5
   =    2  :  10 : 5