# Force needed to pull out a plug out of a drain under water?

• qwertyqwert321
In summary, the force required to remove the plug from the drain of a water tower, located 3.0 m below the surface, with a circular diameter of 5.0 cm and a density of 1000 kg/m3, is 57.624 N. This is calculated using the formula F = pGH * A, where A is the area of the plug, p is the density of water, G is the gravitational constant, and H is the depth of the plug. The atmospheric pressure is cancelled out in this calculation.
qwertyqwert321

## Homework Statement

The plug for the drain of a water tower is located 3.0 m below the surface. The plug is circular and has a diameter of 5.0 cm. If the density of water is 1000 kg/m3 , how much force is required to remove the plug (you may ignore the weight of the plug itself)

A= pi * r ^2
F=P *A

## The Attempt at a Solution

A = pi * r^2 = pi * (0.025)^2 =1.96 * 10 ^-3 m^2

F= pGH * A
= (1000 kg/m3) (9.8) (3.0 m) * 1.96 * 10 ^-3 m^2
= 57.624 N

is this correct? there is no pressure from the atmosphere right?

qwertyqwert321 said:

## Homework Statement

The plug for the drain of a water tower is located 3.0 m below the surface. The plug is circular and has a diameter of 5.0 cm. If the density of water is 1000 kg/m3 , how much force is required to remove the plug (you may ignore the weight of the plug itself)

A= pi * r ^2
F=P *A

## The Attempt at a Solution

A = pi * r^2 = pi * (0.025)^2 =1.96 * 10 ^-3 m^2

F= pGH * A
= (1000 kg/m3) (9.8) (3.0 m) * 1.96 * 10 ^-3 m^2
= 57.624 N

is this correct? there is no pressure from the atmosphere right?
The atmospheric pressure is in addition to the 58N to give the total pressure from above. The pressure from below is just atmospheric. So the atmospheric pressure cancels.

## 1. How does the force needed to pull out a plug out of a drain under water compare to pulling it out in air?

The force needed to pull out a plug out of a drain under water is greater than the force needed to pull it out in air. This is because water has a higher density and viscosity, which creates more resistance against the plug.

## 2. Does the size or shape of the plug affect the force needed to pull it out under water?

Yes, the size and shape of the plug can affect the force needed to pull it out under water. A larger or irregularly shaped plug will create more resistance and require more force to pull out compared to a smaller or streamlined plug.

## 3. How does the depth of the water affect the force needed to pull out the plug?

The depth of the water does not significantly affect the force needed to pull out the plug. As long as the plug is fully submerged, the force required will be the same regardless of the water depth.

## 4. Is there a difference in the force needed to pull out a plug with a smooth surface compared to a rough surface?

Yes, there is a difference in the force needed to pull out a plug with a smooth surface compared to a rough surface. A smooth surface will create less friction with the water, resulting in less resistance and less force needed to pull it out.

## 5. Can the force needed to pull out a plug under water be calculated?

Yes, the force needed to pull out a plug under water can be calculated using the equation F = ρVg, where F is the force, ρ is the density of water, V is the volume of the plug, and g is the acceleration due to gravity. However, this calculation may not be entirely accurate as it does not take into account factors such as surface friction and water turbulence.

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