Select the best answer for the question.

A piston above a liquid in a closed container has an area of [tex]$1 \, m^2$[/tex]. The piston carries a load of 350 kg. What will be the external pressure on the upper surface of the liquid?

A. 27.3 kPa
B. 68.6 kPa
C. 4.90 kPa
D. 3.43 kPa



Answer :

To determine the best answer for the question, let's follow these steps:

1. Identify the parameters:
- The mass of the load ([tex]\( m \)[/tex]) is 350 kg.
- The area ([tex]\( A \)[/tex]) subjected to the load is 1 [tex]\( m^2 \)[/tex].
- The acceleration due to gravity ([tex]\( g \)[/tex]) is 9.8 [tex]\( m/s^2 \)[/tex].

2. Calculate the force exerted by the load:
The force ([tex]\( F \)[/tex]) due to the load is given by the product of the mass and the acceleration due to gravity.
[tex]\[ F = m \times g \][/tex]
Substituting the known values:
[tex]\[ F = 350 \, \text{kg} \times 9.8 \, \text{m/s}^2 = 3430 \, \text{N} \][/tex]
Therefore, the force exerted by the load is 3430 Newtons (N).

3. Calculate the pressure exerted on the liquid:
Pressure ([tex]\( P \)[/tex]) is defined as the force per unit area. It can be calculated using:
[tex]\[ P = \frac{F}{A} \][/tex]
Using the given area:
[tex]\[ P = \frac{3430 \, \text{N}}{1 \, \text{m}^2} = 3430 \, \text{Pa} \][/tex]
Thus, the pressure on the liquid is 3430 Pascals (Pa).

4. Convert the pressure from Pascals to kilopascals:
Since 1 kilopascal (kPa) is equal to 1000 Pascals (Pa), we convert the pressure to kilopascals by dividing by 1000:
[tex]\[ \text{Pressure in kPa} = \frac{3430 \, \text{Pa}}{1000} = 3.43 \, \text{kPa} \][/tex]

5. Conclusion:
The external pressure on the upper surface of the liquid is 3.43 kPa.

Therefore, the best answer for the question is:
D. 3.43 kPa