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Q:

# Which is the weakest force in the universe?

Q:

Is air homogeneous or heterogeneous?

 A) homogeneous B) heterogeneous C) Both A & B D) None of the above

Explanation:

A Mixture is a material made up of two or more different substances which are mixed.

Mixtures can be either homogeneous or heterogeneous.

* A homogeneous mixture is a type of mixture in which the composition is uniform and every part of the solution has the same properties.

* A heterogeneous mixture is a type of mixture in which the components can be seen, as there are two or more phases present.

Air is a homogeneous mixture of the gaseous substances nitrogen, oxygen, and smaller amounts of other substances.

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Q:

Sound waves cannot travel in

 A) Vacuum B) Water C) Glass D) Hydrogen gas

Explanation:

A Sound wave needs a medium for propogation. Hence, Sound cannot travel through a vacuum.

A vacuum is an area without any air, like space. So sound cannot travel through space because there is no matter for the vibrations to work in.

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Q:

Resistance of human body in dry condition

 A) 10 ohm B) 1000 ohm C) 10000 ohm D) 100000 ohm

Explanation:

Under dry conditions, the resistance offered by the human body may be as high as 100,000(10^5) Ohms.

Depending on the person, a rough value for the internal resistance of the human body is 300-1,000 Ohms. The skin's resistance is much lower if it is wet or burnt/blistered.

There are a lot of factors involved and not every person has the same electrical resistance. For instance, men tend to have lower resistance than women.

Within the body, the tissues with the greatest resistance are bone and fat - nerves and muscle have the least resistance.

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0 64
Q:

Q = mc∆T refers to

 A) Enthalpy formula B) Heat Transfer formula C) Specific Heat formula D) Heat of Vaporization

Explanation:

Q = mc∆T refers to Specific Heat formula.

When heat energy is added to a substance, the temperature will change by a certain amount.

The relationship between heat energy and temperature is different for every material, and the specific heat is a value that describes how they relate.

Q = mc∆T

Q = heat energy (Joules, J)

m = mass of a substance (kg)

c = specific heat (units J/kg∙K)

∆T = change in temperature (Kelvins, K)

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0 107
Q:

Acceptable noise level for human ear

 A) > 85 db B) = 85 db C) < 85 db D) None of the above

Explanation:

Sound intensity or level is measured by a unit called a decibel. An 85 decibel noise level is not a safe standard for the public.

Hence, Acceptable noise level for human ear is less than 85 db.

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0 64
Q:

Atmospheric pressure exerted on earth is due to

 A) gravitational pull B) rotation of earth C) revolution of earth D) uneven heating of earth

Explanation:

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.

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1 197
Q:

The modulus of elasticity for mild steel is approximately equal to

 A) 210 kN/mm2 B) 100 kN/mm2 C) 80 kN/mm2 D) 10 kN/mm2

Explanation:

It is useful to have a property of a material that is independent of the size of the sample and can be use to compare its elastic properties with another - this is called the Modulus of Elasticity for the material.

The modulus of elasticity is defined as:

Modulus of elasticity = Stress / Strain

There are three types of moduli. They are :

(a) the Young Modulus - tensile and compression longitudinal stress

(b) the shear modulus - a shearing stress

(c) the bulk modulus - volume changes of the specimen.

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0 112
Q:

What causes brownian motion in colloids?

 A) coagulation of particles and the dispersed phase B) erratic flashes of light C) molecules of the dispersion medium colliding with dispersed phase particles D) All the above

Answer & Explanation Answer: C) molecules of the dispersion medium colliding with dispersed phase particles

Explanation:

When their is a colloid in the solution, then it will show the Brownian movement, such as dust particle in the air will show the Brownian movement.

Hence, Brownian movement arises due to the impact of the molecules of the dispersion medium with the colloidal particles. It has been postulated that the impact of the molecules of dispersion medium on the colloidal particles are unequal.

This leads to the zig-zag (random) motion of the colloidal particles.