TyroCity: Physics XI Notes

Does a ship sink more in river water or in sea water? Explain.

Physics XI Notes — Sun, 18 Aug 2013 05:41:42 +0000

A ship sink more in river water than in sea water because the density of sea water is more than that of river water due to the presence of impurities.

why do we slip on a rainy day?

Physics XI Notes — Sun, 18 Aug 2013 05:41:42 +0000

In rainy day, the rain water forms a layer on the road. This layer works as a lubricant which decreases the friction. Due to less friction, we slip on rainy day.

Thermal Properties of Matter- Old is Gold

Physics XI Notes — Sun, 18 Aug 2013 05:41:42 +0000

Which has more atoms: a kilogram of hydrogen or a kilogram of iron?
Molecules of different gases have equal average kinetic energies, provided their temperature is the same. Do these molecules have equal velocities also?
Outline the essential features of the kinetic theory of gases.
Why do you consider an ideal gas while formulating the pressure in the light of kinetic theory of gases?
Why does the cycle tube burst sometimes in summer?
At absolute zero temperature, why the kinetic energy is zero?
Under what conditions do the real gases obey more strictly the gas equation PV=RT?
Write the unit of the universal gas constant and give its physical meaning.
In the kinetic theory of gases, why do we not take into account the changes in gravitational potential energy of the molecule?
Absolute zero temperature is not zero energy temperature. Explain.
What are the characteristics of a gas to be an ideal?

What is meant by elastic and inelastic collision?

Physics XI Notes — Sun, 18 Aug 2013 05:41:42 +0000

The collision in which total linear momentum and total K.E. is conserved is called elastic collision.

i.e. In elastic collision,

m1u1 + m2u2 = m1v1 + m2v2

½(m1u1²+ m2u2²) = ½(m1v1² + m2v2²)

Eg: Collision between atomic or sub-atomic particles, collision between gas molecules, etc.
The collision in the total linear momentum is conserved but the total K.E. is not conserved is called inelastic collision.
i.e. In inelastic collision,

m1u1 + m2u2 = m1v1 + m2v2
But,
½(m1u1² + m2u2²) ≠ ½(m1v1² + m2v2²)

Eg: A bullet embedded in a target is one example of inelastic collision.

Is friction a necessary evil? Explain.

Physics XI Notes — Sun, 18 Aug 2013 05:41:42 +0000

Yes. Friction is the necessary evil because,

(a) Without friction between the feet and the ground, it would not have been possible to walk.

(b) The tyre of the motor cars and cycles are rough to increase the friction.

If a moving bullet striking a block of wood on a frictionless table embeds inside it what happens to the KE of the bullet?

Physics XI Notes — Sun, 18 Aug 2013 05:41:42 +0000

The K.E. energy of the bullet is converted into sound and heat energy.

Work

Physics XI Notes — Sun, 18 Aug 2013 05:41:42 +0000

Work is said to be done if a force displaces any object in any direction other than 90˚ to the direction of force applied.
If ‘F’ be the force applied and ‘d’ be the displacement and ‘θ’ be the angle between ‘F’ and ‘d’, work done by the force is,
W = Fcosθd
= Fdcosθ
W= F.d
Work is a scalar quantity. Its SI unit is Joule.

a) When the angle between F and d is acute, the work done by the force is positive.
Eg:- Pushing a duster moves the duster in the direction of force. So θ=0˚ then,
W = Fdcosθ
= Fcos0˚
= Fd [Work is positive]

b) When the angle between F and d is 90˚, the work done is zero.
Eg:- A coolie carry a load and walking on horizontal road does no work because the direction of force is vertical while he moves in horizontal direction. So,
W = Fdcos90˚
= 0

c) When the angle between F and d is 90˚<θ≤180˚, then work done is negative.
Eg:- When a body is pushed, it moves in the direction of force. Work done by the force is positive but the work done by friction is negative.
W = Frdcos180˚
= -Frd

Capacitance and dielectrics- Old is Gold

Physics XI Notes — Sun, 18 Aug 2013 05:41:42 +0000

Distinguish between dielectric constant and dielectric strength.
Distinguish between polar and non-polar dielectrics.
Define dielectric constant and dielectric strength.
How will you arrange 3 capacitors each having capacity of 2µF, to get a capacitor of capacity 3µF?
Is dielectric constant, the same as dielectric strength? Explain with example.
Explain how the capacitance of a parallel plate capacitor can be increased.

Photometry- Old is Gold

Physics XI Notes — Sun, 18 Aug 2013 05:41:42 +0000

Why does the illuminance of a surface decrease as it moved away from the light source?
What is the meaning of Luminous intensity?
Define luminous flux. State its unit of measurement.
What are the factors on which the illuminance of a surface depends?
Define luminous efficiency of a source of light and give its SI unit.
What is the difference between lumen and lux?
Define illuminance. Name the factor upon which it depends.
The sun is less bright in morning and in evening as compared to that at noon although its distance from the observer is almost the same. Why?
Distinguish between illuminance and luminance.

Hygrometry- Old is Gold

Physics XI Notes — Sun, 18 Aug 2013 05:41:42 +0000

Why are dews formed in the early morning hours?
Define due point.
Define triple point.
Why is the triple point of water chosen as a standard fixed point in modern thermometry?
Distinguish between saturated and unsaturated vapour pressure.
Distinguish between a gas and vapour.
What is relative humidity? Why is its value more near the sea shore?