Tissues — Science STD 9 — Question

Air is a mixture of:

1. Nitrogen, oxygen, methane, carbon dioxide.
2. Nitrogen, oxygen, carbondioxide, water vapours.
3. Nitrogen, carbon dioxide, oxygen, carbon monoxide.
4. Nitrogen, oxygen, carbon monoxide, water vapours.

When a wave travels from the one medium to another, the quality which will not change is its:

An apple of mass 100g falls from a tree because of gravitational attraction between the earth and the apple. If the magnitude of force exerted by the earth on the apple be F₁, and the magnitude of force exerted by the apple on the earth be F₂, then:

1. F₁ is very much greater than F₂
2. F₂ is very much greater than F₁
3. F₁ is only a little greater than F₂
4. F₁ and F₂ are exactly equal.

Lactation period is maximum in:

1. Frieswal
2. Sahiwal
3. Holstein-Friesian.
4. Karan-Swiss.

When a body is going upwards vertically the acceleration due to gravity is taken as

Sun causes weathering of rocks through:

1. Mechanical force.
2. Physical phenomena.
3. Chemical changes.
4. Biological changes.

An element which can exhibit valencies of 2, 4 and 6 can be:

1. Copper.
2. Iron.
3. Mercury.
4. Sulphur.

The time taken to complete one oscillation is called.

The splash is heard 2.05s after the stone is dropped into a well of depth 19.6m.The velocity of sound is?