AIM OF THE EXPERIMENT: To show that the weight of objects changes in water.
MATERIALS: thick string, scissors, a ruler, two washers, a pencil, a table, adhesive tape, a felt-tip pen, three 250 ml glasses.
MATERIALS: thick string, scissors, a ruler, two washers, a pencil, a table, adhesive tape, a felt-tip pen, three 250 ml glasses.
Изображение
Cut two pieces of string 30 cm long and tie them to the ends of the pencil.
Tie a washer to each free end of the string.
Cut another piece of string 60 cm long, tie one end of it to the middle of the pencil and fix the other to the edge of the table with adhesive tape.
Move the string that holds the pencil until you find the position in which the pencil is parallel to the floor. The washers should then be about ten centimetres above the floor.
Using the felt-tip pen and the adhesive tape, label the glasses A and B.
Stand the empty glasses on the floor so that the washers on their strings hang down into them.
Fill the third glass with water and begin pouring the water slowly into glass A.
RESULTS: When the water covers the washer, that washer rises and the pencil tilts. The washer in the empty glass goes down.
WHY? The Earth's gravity acts on every object and is directed towards the centre of the Earth. That is what gives objects their weight. The glasses look empty, but in fact they are full of air. In air both our washers weigh the same, but once one of them is placed in water a buoyancy force begins to act on it. As a result the force with which that washer is attracted to the Earth is reduced. The balance is upset, and the washer in the empty glass starts to go down.
METHOD:
Tie a washer to each free end of the string.
Cut another piece of string 60 cm long, tie one end of it to the middle of the pencil and fix the other to the edge of the table with adhesive tape.
Move the string that holds the pencil until you find the position in which the pencil is parallel to the floor. The washers should then be about ten centimetres above the floor.
Using the felt-tip pen and the adhesive tape, label the glasses A and B.
Stand the empty glasses on the floor so that the washers on their strings hang down into them.
Fill the third glass with water and begin pouring the water slowly into glass A.
RESULTS: When the water covers the washer, that washer rises and the pencil tilts. The washer in the empty glass goes down.
WHY? The Earth's gravity acts on every object and is directed towards the centre of the Earth. That is what gives objects their weight. The glasses look empty, but in fact they are full of air. In air both our washers weigh the same, but once one of them is placed in water a buoyancy force begins to act on it. As a result the force with which that washer is attracted to the Earth is reduced. The balance is upset, and the washer in the empty glass starts to go down.
METHOD: