Define pressure - Leaving Cert Physics - Question 1 - 2013

To demonstrate atmospheric pressure, you can conduct a simple experiment involving a can and water:

1. Apparatus: Use a can filled with water and place a cardboard lid over it.
2. Procedure: Carefully invert the can so that the cardboard lid remains in place, and then remove the lid slowly.
3. Observation/Conclusion: As the cardboard lid is removed, the can remains intact, demonstrating that air pressure acting on the lid supports the weight of the water, illustrating that the atmosphere exerts pressure.

To calculate the decrease in pressure as the diver ascends from 50 m to 20 m:

1. Pressure at 50 m:

   $P_{50} = \rho g h = 1000 \times 9.8 \times 50 = 490000 \, \text{Pa}$

2. Pressure at 20 m:

   $P_{20} = \rho g h = 1000 \times 9.8 \times 20 = 196000 \, \text{Pa}$

3. Decrease in Pressure:

   $\Delta P = P_{50} - P_{20} = 490000 - 196000 = 294000 \, \text{Pa}$

Thus, the decrease in pressure on the diver as she swims upwards is 294,000 Pa.