Give Scientific Reason.

Question 13 Marks

Work done on an artificial satellite by gravity is zero while moving around the earth.

Answer

When the artificial satellite moves around the earth in a circular orbit, gravitation force acts on it.
The gravitational force acting on the satellite and its displacement are perpendicular to each other. i.e. 0 = 90°
For 0 = 90°, work done is zero. [ v cos 90 = 0)
Hence, work done on an artificial satellite by gravity is zero while moving around the earth.

Question 23 Marks

An exploding firecracker lights up as well as makes a sound.

Answer

The exploding firecracker converts the chemical energy stored in it into light and sound respectively.
Here, energy is converted from one type to another.
Hence, an exploding firecracker lights as well as makes a sound.

Question 33 Marks

Wind can move the blades of a windmill.

Answer

Wind has certain energy.
When it hits the windmill energy is transferred to the windmill because of which it moves.
Hence, wind can move the blades of a wind mill.

Question 43 Marks

A stretched rubber band when released regains its original length.

Answer

Question 53 Marks

Flowing water from some height can rotate turbine.

Answer

Flowing water has certain energy.
When it hits the turbine, energy is transferred to the turbine, because of which it rotates.
Hence, flowing water from some height can rotate a turbine.

Question 63 Marks

A moving ball hits a stationary ball and displaces it.

Answer

The moving ball has certain energy.
When it hits the stationary ball, the energy is transferred to the stationary ball, because of which it moves.
Hence, a moving ball hits a stationary ball and displaces it.

Science Give Scientific Reason.