Forces and Water

We have been looking at the forces that exist in the world around us and last week we investigated water resistance.

We discovered that water resistance or upthrust works in the opposite direction to gravity and this is why some objects float.

Getting cubes to float in water

Putting in the cubes carefully

We then added salt to the water and discovered that salt water will allow more cubes to be added before the container sank.

Adding the salt

We also experimented with finding out if other liquids had more upthrust than water. We measured objects using force meters. We measured the weight of the objects in the air, in water and when they were suspended in oil. It was very messy!

Weighing objects suspended in water

Weighing objects in oil

We discovered that the objects weighed less when they were in the water or oil than if they were just in the air. The oil made a bit of difference to the weight of the object so oil has more upthrust than plain water.