Week 4 - Do all heavy things sink? 

In our lesson this week, we will be considering why objects float or sink. We will be learning about a new force, upthrust.

Watch this clip in the link below to learn about upthrust: 

What is happening when a boat floats?

Floating ships

When an object is placed in the water, it displaces the water (moves it out of its place; like when you climb into the bath). This displaced water is pushed upwards and to the side of the object. However, the water doesn't ‘want to be there’ because gravity is trying to pull it back down underneath the object. This creates an upward reaction force called UPTHRUST.

If weight and upthrust are balanced forces (are the same size as each other) or if the weight is less than the upthrust, an object will float.

To float an object must displace (push out) its own weight in water so that that water can push back against the boat with the same force as the downward pull of gravity.

Please watch the video below.

Please complete one of the tasks below, depending on your situation and the equipment you have available.

Task (Option 1): Weigh out a 10g ball of play dough or plasticine. Drop the ball shaped plasticine/play dough in a jug of water. What happens? Now change its shape. Can you make it float? Once it is floating, add some cargo to your boat, beads or frozen peas will do the trick. How many does your boat hold before it sinks? Can you change the design to hold even more cargo? Write an account of what you did and how much cargo you managed to carry. You can present this in any way you like adding photos too, then send it to me on Teams please.

Task (Option 2): Please describe the experiment which the children in the video did. Write up your experiment with the following subtitles please - What question were they trying to find the answer for? What did each group actually do in their experiment? What was different about each groups experiment? What did the children discover when they put all their results together in a graph? What was the answer to the original question involving the treasure?