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**Top 100 FAQ - Physics Oneliner Key Points**

This Article is All About the

**Basic Facts and Figures on Mechanics**. Here we Include**Top 100 Frequently Asked Questions (FAQ)**on**Physics**from where basic questions were generally asked. Here we listed all Important Points based on**Oneliner**so it would be easy for you to Notedown these points. All**Basic Scientific Facts**are important for**SSC CGL 2018, CHSL Exams, CDS, NDA, IB, Railway Exams.****SCIENCE & TECHNOLOGY**

- The number of basic
**SI**unit is**7.** **One Fermi**meter is equal to**10^ (-15) m.****Fermi**is the most suitable unit to express the nuclear radius.**Light year**is the**unit of distance.****Parasec**is the**unit of Distance.****1 Astronomical unit**is the average**distance****between Earth and Sun.****Erg-Sec**is the unit of**Planks’s Contant.****Volt/ Ampere**is the unit of**resistance.**- If the density of water is
**1g/cm^3**in**CGS system**, thn its value in**MKS system**is**10^3 Kg/m^3.** **Potential**is measured in**Joule/ Coulomb.****Maxwell**is the unit of**Magnetic Flux.****Weber is the SI unit of Magnetic Flux.****One Light year**is equal to approximately**10^16 m.****Ampere**is the unit of**Current electricity.****Newton/m^2**is the**SI unit of Young’s Modulus of elasticity.****Curie**is the unit of**Radioactivity.****Decibel**is the unit of**intensity of sound.**- In the relation
**α = βt + λ,**λ and α are measured in metre (m) and t is measured in second. The SI unit of β must be m/s. **Steradian**is the unit of**Solid Angle.****SI Unit of Surface Tension**is**N/m.**- The
**SI unit of angular momentum**is**Kgm^2/S.**

- A bus covers the first half of its distance with speed v1 and the second half with speed v2. The average speed during the whole journey is 2v1v2/ (v1 + v2).
- A bus travels for a certain time. Its speed during the first half time is v1 and during the second half time is v2. The average during the whole journey is (v1 + v2) / 2.
**When milk is churned****vigorously**the cream from it is separated out due to**Centrifugal Force.**- A passenger in a moving train tosses a coin upward which falls behind him. It implies the motion of the train is accelerated.
**The first law of Newton**gives the**definition of force.****Distance of stars**is measured in**Light year.**- Five equal forces of 10N each are applied at one point and all are lying in one plane. If angles between them are equal, the resultant of these forces would be 0.
- Masses of stars and galaxies are expressed as solar mass usually.
**An object with a constant speed might be accelerated.**- When a body is accelerated, its speed may or may not be changed.
- Dirty cloths containing grease and oil are cleaned by adding detergents to water. The detergents reduce drastically the surface tension between water and oil and strains are removed.
- Motion of a oscillating liquid column in a U-tube is periodic but not simple harmonic.
- A monkey sits on the pan of a spring scale kept in an elevator. The reading of the spring scale would be maximum when the elevator accelerates upward.
- A ball is thrown vertically upwards assuming the air resistance to be constant and considerable, the time of ascent < time of descent.
- A man in a train moving with constant velocity drops a ball on the platform. The path of the ball seen by an observer standing on the platform is a parabola.
- Two masses, each equal to m are attached to one another by a mass less string passing over a smooth pulley the tension in the string is mg.
- A car accelerates from rest with acceleration 1.2m/s^2. A bus moves with constant speed of 12m/s in a parallax lane. The car then would take 20s from its start to meet the bus,
- The value of specific gravity remains same in all system of units.
- 2 teams are pulling a rope with equal and opposite forces each of 5KN in a tug of war so that a condition of equilibrium exists. The tensile force in the rope would be 5KN.
- A body moves with a constant speed along a curved path in acceleration is perpendicular to its velocity.
- Under non contract forces electrostatic and gravitational forces come. If the KE of a body is increased by 300%, the momentum would increase 100%.
- If the momentum of a body is increased by 50%, then its KE would increase to 125%.
- A body is lifted by a man to height of 1m in 30 s. Another man lifts the same mass to the same height in 60 s. Then the work done by them are in 1:1 ratio.
- The distance between two crests in a wave is given by wavelength.
- If a bomb dropped from an airplane explodes in mid-air, its KE (Kinetic Energy) increases.
- A light body A and a heavy body B have equal KE of transaction. Then B has larger momentum than A.
- When two bodies stick together after collision, it is said to be completely inelastic.
- A bullet hits and gets embedded in a solid block resting on a horizontal friction less table. Then momentum is conserved.
**A rocket works**on the principle of**conservation of linear momentum.****A particle revolves round a circular path with a constant speed the acceleration of the particle is along the radius.**- Roadways are banked on curves so that the wear and tear of tyre may be avoided.
- If a gymnast, standing on a rotating stool with his arms and stretched, suddenly lowers his arm his angular velocity remains constant.
- When the external torque on a system is zero, there will be the conservation of its total energy.
- If the radius of the earth were shrink by 1%, its mass remaining the same, the value of g on the earth’s surface would increase by 2%/
**The weight of the body at the center of the earth is 0.**- Weightlessness experienced in spaceship is due to absence of gravity.
- Satellite having same orbital period as the period of rotation of the earth about its own axis is known as Geostationary satellite.
- Two satellites are moving in the same circular orbit around the earth, they must have the same speed.
- If the distance between the masses is doubled, the gravitational attraction between them is reduced to a quarter.
- The ratio of inner mass to gravitational mass is
**equal to 1.** - The intensity of the earth’s gravitational field is maximum at the pole.
- The period of a satellite in a circular orbit of
**Radius R is T.**The period of another satellite in circular orbit of radius**4R is 8T.** - The escape velocity from the earth’s surface does not depend on mass of the body.
- If the radius of the earth’s orbit becomes one-fourth of the present value, the deviation of one year will become 1/8 times.
**If the earth were to stop rotating, the value of g increases.****If we move from equator to pole, the value of g increases.****As we go from the equator to the poles, the value of g increases.**- A satellite revolves around the earth in elliptic orbit, its speed is greatest when it is closest to earth.
- If the
**diameter and mass of the earth**becomes two times their present values, then the weight of an object on the surface of the earth will become half. - A
**Geostationary satellite**has an**orbital period of 24 hours.** **Cavendish**provided the**first experimental value of G.**

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