State the unit of pressure - Leaving Cert Physics - Question b - 2014

To demonstrate that the atmosphere exerts pressure, an experiment can be set up using a glass of water and a piece of cardboard.

1. Apparatus: Gather a glass of water and a piece of cardboard.
2. Procedure: Fill the glass with water and place the cardboard over the top. While holding the cardboard in place, quickly invert the glass.
3. Observation/Conclusion: The cardboard holds the water inside the glass despite gravity acting on the water. This is due to atmospheric pressure acting on the cardboard, which prevents the water from falling out.

Archimedes' principle states that the upthrust (buoyant force) on a body immersed in a fluid is equal to the weight of the fluid that is displaced by the body.

The upthrust (buoyancy force) acting on the object submerged in the liquid is equal to the weight of the liquid displaced. In this case, the reading shows 3 N, which indicates the upward force exerted by the liquid on the object.

The object will not float in the liquid if released because its weight (10 N) is greater than the upthrust (3 N) acting on it. Since the weight exceeds the buoyant force, the object will sink. Additionally, if it is more dense than the liquid, it will not float.