Practice MCQ Questions and answers on General Science - Physics MCQs

The Vernier caliper has a main scale and a sliding vernier scale which can measure nearest to 0.02 mm. It can be used to measure internal and the external dimensions of an object by using the smaller jaws at the top and the main jaws respectively. By using stems depth can be measured.

The first statement is incorrect because light takes 1.2 – 1.3 seconds to reach from moon to earth. Second statement is correct. The exact time taken is 8 min 19 seconds (Speed of light=300,000 kilometres per second mean distance of sun from Earth=14,96,00000 Kms . The time comes to be about 498.66 second.) Statement 3 is also incorrect. The first part of the statement is correct which says that It takes 4.22 years for the light to reach from the nearest star, however nearest star is Alpha proxima and not Alpha Centauri is not nearest. Nearest is Proxima Centauri and to reach from Alpha centauri it takes 4.40 years. Next is Barnard`s Star, which is 5.94 light years away from Earth.

The joule is the unit of energy in the International System of Units. It is equal to the work done on an object when a force of one Newton acts on that object in the direction of the force’s motion through a distance of one meter. One joule of work is said to be done when a force of 1 N causes a displacement of 1 m.

Mica and sulphur are insulators

Both are correct statements

If we need a satellite for the purpose which needs this satellites to remain at a particular distance from earth at all the time, then we need circular orbits so all the points on circular orbit are at equal distance from earth’s surface. The circular equatorial orbit is exactly in the plane of equator on the earth. If the satellite is moving in the circular-equatorial orbit and its angular velocity is equal to earth’s angular velocity, the satellite is said to be moving along with the earth. This satellite would appear stationary from the earth and this orbit would be called Geostationary Orbit. Thus the features of geostationary satellite are as follows:
The orbit is circular
The orbit is in equatorial plane i.e. directly above the equator and thus inclination is zero.
The angular velocity of the satellite is equal to angular velocity of earth
Period of revolution is equal to period of rotation of earth.
Finish one revolution around the earth in exactly one day i.e. 23 hours, 56 Minutes and 4.1 seconds
There is ONLY one geostationary orbit.
Geosynchronous But here, we need to understand the difference between the geostationary and geosynchronous orbits. We should note that while other orbits may be many, there is ONLY ONE Equatorial orbit, i.e. the orbit which is directly above the earth’s equator. Sometimes we send a satellite in the space which though has a period of revolution is equal to period of rotation of earth, but its orbit is neither equatorial nor Circular. So, this satellite will finish one revolution around the earth in exactly one day i.e. 23 hours, 56 Minutes and 4.1 seconds, yet it does NOT appear stationary from the earth. It looks oscillating but NOT stationary and that is why it is called Geosynchronous. So, the main features of a geosynchronous satellite are as follows:

The orbit is NOT circular
The orbit is NOT in equatorial plane i.e. directly above the equator, it’s in inclined orbit
The angular velocity of the satellite is equal to angular velocity of earth
Period of revolution is equal to period of rotation of earth.
Finish one revolution around the earth in exactly one day i.e. 23 hours, 56 Minutes and 4.1 seconds
There are many geosynchronous orbits.
Please note that it is practically NOT possible to achieve an absolute geostationary orbit. So, the terms geostationary and geosynchronous are used alternatively

?-particles
They are doubly ionised helium nuclei having a mass equal to 6.64 × 10–27 kg and charge equal to 3.2 × l0–19 C.
They have the highest ionising power.
They have the least penetrating power.
They produce fluorescence in the zinc sulphide screen.
?-particles.

They are negatively charged particles, having a charge equal to –1.6 × 10– 19 C and mass 9.1 × 10–31 kg.
They have more penetration power than ?-particles.
They have less ionising power than ?-particles.
They affect photographic plate.
?-radiations

They are electromagnetic waves, having wavelength less than 0.01 Å.
They have a very high penetration power.
They have a very low ionising power.
They are not affected by electric or magnetic fields.
Notes on Ionising power If one unit is ionising power of ?-radiations, then 100 units is ionising power of ?-particles and 10000 units is the ionising power of ?-particles. Notes on Penetration power ?-radiations can penetrate even 30 cm of iron. ?-particles can penetrate 1mm of lead or 5 mm of aluminium. ?-particles can penetrate 2.7 to 8.6 cm of air

Oscillation of the atoms and molecules, Entropy, Electrical resistance none of them cease to exist at Absolute zero temperature on Kelvin scale.

The velocity of an object undergoing uniform circular motion is always changing (because the direction is always changing). Further, since the acceleration is centripetal, it must always point toward the center of the circle; so, as the object moves around the circle, the acceleration vector is also constantly changing direction. Notice that for an object in uniform circular motion, both the velocity and the acceleration are changing because the directions of these vectors are always changing, even though their magnitudes stay the same. In this question, only speed remains unchanged.

A Balloon filled with a gas such as Hydrogen gas is much lighter in weight than the weight of air displaced by it. So the buoyant force exerted by the air on a balloon is greater than the weight of the balloon. The hydrogen gas which is lighter than air enables the balloon to float.