Physics Test - 59

On the Kelvin scale ,the melting point of ice is273K.

Fog is tiny water droplets or ice crystals suspended in the air at or near the Earth's surface. Hence, fog is an example of a colloidal system liquid dispersed in gas.

The quality of sound produced by an instrument depends on the Number of overtones.

An atom bomb based upon the principal of Nuclear fission.

Graphite is a covalent-network type of crystalline solid.

At the Curie temperature, the ferromagnetic materials get converted into Paramagnetic materials.

The atmospheric pressure at the surface of the Earth is due to gravitational pull of the earth and is about 14.7 psi.

That means that the weight of a column of air which has a cross section of 1 square inch and which stretches from the surface of the Earth to space is 14.7 pounds.

Water has the maximum density at 4^oC. So at this temperature, it sinks down to bottom and stays here. If it cools further, it will become less dense and move up. So while the upper layers can cool enough to form ice, the bottom layers remain as water at 4^oC .

The interval between object pass the same point is 4 sec.

That means in 2 sec, object reaches the top and in next 2 sec, it again reaches the same point.

By the info given, we can find the velocity of that point by using : v=u+(-gt)

0= u - 10×2

u = 20

Then the velocity at 25m is 20m/sec.

so the initial velocity is

−v² = u² + (−2gh)

400 = u² − 2x 10 x 25

u² = 900

=> u = 30 m/s

Alcohol has a freezing point as low as −117^oC. So it won't freeze even in very cold countries.