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With the help of an activity prove that the force acting on a smaller area exerts a larger pressure?

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With the help of an activity prove that the force acting on a smaller area exerts a larger pressure?

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Consider a block of wood kept on a table top. The mass of the wooden block is 5 kg. Its dimension is 40 cm x 20 cm x 10 cm.

Now, we have to find the pressure exerted by the wooden block on the table top by keeping it vertically and horizontally.

The mass of the wooden block = 5 kg

Weight of the wooden block applies a thrust on the table top

Thrust = F = m x g

= 5 kg x 9.8 m/s2 = 49 N

Case a: When the wooden box is kept vertically with sides 20 cm x 10 cm.

Area of a side = length x breadth

= 20 cm x 10 cm

= 200 cm2 = 0.02 m2

Pressure = \(\frac{Thrust}{Area}\) = \(\frac{49 N}{0.02 m^2}\) = 2450 N/m2

Case b: When the block is kept horizontally with side 40 cm x 20 cm

Area = length x breadth

= 40 cm x 20 cm

= 800 cm2 = 0.08 m2

Pressure = \(\frac{Thrust}{Area}\) = \(\frac{49 N}{0.08 m^2}\) = 612.5 N/m2

∴ The pressure exerted by the box in case (a) is more as compared to the pressure exerted in case (b).

The area is reduced and the pressure exerted is more.
This shows that pressure ∝ 1/area.

Pressure will be larger if the area is reduced.

Application:

  • Nails have pointed tips.
  • Knives have sharp edges.
  • Needles have pointed tips.
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