# Videos

#### Cave

Caves are underground hollows, formed by natural processes, with a depth of at least 2m. Prehistoric humans often used them as shelters.

#### The rock cycle

Due to the effect of both exogenic and endogenic forces, rocks constantly change. This is called the rock cycle.

#### Igneous rocks

Igneous rocks, like andesite and basalt, are formed when erupting lava solidifies on the surface. Due to erosion over millions of years signs of past...

#### Plotting parallel lines – Solution II

Let’s construct a rhombus such that one of its sides lies on line e and point P is one of the vertices on the opposite side.

#### Dog tricks

Man's most loyal friend is the dog. They are excellent at guarding houses and can also be taught to perform minor tricks for us, too.

#### Sarcophagus

The recording shows a more than 2000-year-old gilded sarcophagus. You can see the names of the deceased and his protecting gods on the coffin.

#### 35mm cinema projector

Watch this video to learn how a cinema projector works and how a film appears on the screen.

#### Reflecting a circle across an axis

Axis t and a circle with centre O and radius r are given on a particular plane. Let’s plot the mirror image of the circle.

#### The hot ice experiment

The words hot and ice together? There must be a trick somewhere. Let’s have a look.

#### Plotting a perpendicular to a line at a given point P on the line

Both line e and point P, which is situated on it, are given. Let’s plot line g to include point P on line e so that it is perpendicular to line e.

#### Plotting a perpendicular on a line from a point P that is not on the line

Both line e and point P, which is not situated on line e, are given. Let’s plot line g such that it passes through point P and is perpendicular to line e.

#### Archimedes' seesaw

In this experiment, we use buoyancy to study the balance of two glasses of water.

#### Plotting parallel lines – Solution I

Let’s plot line g such that it is parallel to line e and passes through point P.

#### Reflecting a line segment across an axis

Axis t and line segment AB are given on a plane. Let’s plot the mirror image of line segment AB across t.

#### Archimedes’ principle with gases

Is there a difference between the weight of a plastic bottle filled with air and the weight of a crushed one?

#### Constructing the perpendicular bisector of a line segment

Let’s construct the perpendicular bisector of a 6-cm-long line segment.