Question

A block of wood of mass 6kg and dimensions 50cmX30cmX20cm is palced on a table top.find the pressure exerted if the block lies on the table top with sides abd dimensions:(g=10m/s^2). a)50cm X 30cm. b) 30cm X 20cm

Answer 1

Pressure = force / area 

So the bigger the area, the LOWER the pressure. For maximum pressure, the block therefore needs to be standing on a face with the SMALLEST area. 

In this case, that's the face that measures 3 cm * 2 cm. 

Now we need to sort out the units. The SI unit of pressure is the pascal {N/m²} So we need to convert the area of the face into square metres. 

Area = 3 cm * 2 cm = 0.03 m * 0.02 m = 0.0006 m² 

The force acting is just the weight force of the block. 
weight = mg 
where m is the mass and g is the acceleration due to gravity { g = 9.81 m/s² } 

weight force = 0.0216 kg * 9.81 m/s² = 0.212 N 

Maximum pressure = 0.212 N / 0.0006 m² = 353 Pa {rounded} 


2. Pressure (P) at the base of a column of liquid of height h and density ρ is given by 

P = ρgh 

Watch the units again! 
ρ for water = 1000 kg/m³ 
h = 250 cm = 2.5 m 
g = 9.81 m/s² 

P = 1000 * 9.81 * 2.5 
P = 24525 Pa

Answer 2

ans is 24525 pa . hope this will help you