JEE-Main - Grade 11 - Physics - Gravitation - Importance and Snapshot of Gravitation - Study ref# 712

Introduction:
Early in our lives, we become aware of tendency of all
material objects to be attracted towards the earth, going uphill is lot more
tiring than going downhill and there are many other such phenomena.
Historically it was t... read more

JEE-Main - Grade 11 - Physics - Gravitation - Importance and Snapshot of Gravitation - Study ref# 713

Following sections must be covered to understand
Gravitation:
1. Introduction
2. Kepler’s laws
3. Universal law of gravitation
4. The gravitation constant
5. Acceleration due to gravity of the earth
6. Acceleration due to gra... read more

JEE-Main - Grade 11 - Physics - Gravitation - Target Setup for Gravitation - Study ref# 714

Student requires to achieve the following milestones to get better grip over Gravitation. The milestones / targets are as follows:- Starting Point: Days 0Test TypeAppear on TestTarget TestsScorePractice Test000%Chapter Test000%Su... read more

JEE-Main - Grade 12 - Physics - Electrostatic Potential and Capacitance - Introduction and Snapshot of Electrostatic Potential and Capacitance - Study ref# 809

Introduction:
In Chapters 6 and 8 (Class XI), the
notion of potential energy was introduced. When an external force does work
in taking a body from a point to another against a force like spring force or
gravitational force, that work ... read more

JEE-Main - Grade 11 - Physics - Motion in a Plane - Study ref# 166

Two particles are dropped from top of a tower with an interval of 2 sec. Find the relative velocity and relative acceleration of the particles. Gravitational acceleration is g m/s2 Answer: When the first particle moves downward by 2 sec, the second p... read more

JEE-Main - Grade 11 - Physics - Motion in a Plane - Study ref# 167

Derive the equation of motion of a particle which is projected with velocity u and at an angle with horizontal. Answer: Suppose that, the particle is launched with velocity u that makes angle with the x-axis. So, compo... read more

JEE-Main - Grade 11 - Physics - Work, Energy and Power - Study ref# 325

Can mechanical energy be negative? What does negative energy signify? Give an example. Answer: As mechanical energy = Kinetic energy + Potential energyFor mechanical energy is negative, potential energy should be negative and magnitude will be g... read more

JEE-Main - Grade 11 - Physics - Work, Energy and Power - Study ref# 330

What are conservative forces? Distinguish the conservative and non – conservative forces among the following: a) Gravitational force b) Frictional force c) Air resistance d) Electrostatic force Answer: Conservative forces those forces in which wor... read more

Give two characteristics of gravitational force Answer: 1) Conservative force 2) Central force (acts along the line joining the two bodies)... read more

If the earth is regarded as a hollow sphere, then what would be the weight of an object at some depth below the earth’s surface? Answer: zero... read more

What is a parking orbit? Answer: It is the orbit of a satellite in which the period of revolution of the satellite is equal to the period of rotation of the earth about its axis.... read more

If the diameter of the earth becomes double and the mass being unchanged, how the weight of a body at the earth’s surface would be affected? Answer: And So, So the weight will become one fourth of its initial value... read more

Why does a body weigh more at poles than the equator? Answer: The value of the gravitational acceleration g, is more at poles than the equator. This makes a body weigh more at poles.... read more

Why does the earth have atmosphere but the moon does not? Answer: The escape velocity from the earth surface is about 11.2 km/sec which is greater than the r.m.s. velocity of the air molecules. The escape velocity from the moon’s surface is about 2.4... read more

How much energy is required to keep a satellite orbiting? Neglect the sir resistance. Answer: No energy is required. The centripetal force is provided by the gravitational force and the work done by it is zero.... read more

Should the speeds of two artificial satellites of the earth having different masses but the same orbital radius, be same? Answer: Yes, since orbital velocity is independent of the mass of satellite. ... read more

What is escape speed? Derive an expression for it. Answer: The minimum velocity required to escape from the gravitational force of the earth is called escape velocity. Total energy is the sum of P.E. and K.E., To escape K.E. should b... read more

What is the angular velocity at any point on the equator so that the body feels weightlessness? Answer: At any point on the surface of the earth, the acceleration due to gravity is, For equator, α=0 . To feel weightlessness g'Therefore... read more

State the universal law of gravitation. Establish the relationship where Me and Re are the mass and radius of the earth respectively. Answer: Universal law of gravitation: Everybody in this universe attracts every other body w... read more

The radius of the earth is reduced by 4%. The mass of the earth remains unchanged. What will be the change in escape velocity? Answer: Escape velocity, say v, is given by Differentiate w.r.t ‘R’, we get, ------... read more

The radii of two planets are R and 2R respectively and their densities P and P/2 respectively. What is the ratio of acceleration due to gravity at their surfaces? Answer: ... read more

What is the effect of rotation on the value of ‘g’? Derive the relation. Answer: Consider a mass m placed at a latitude θ. Two forces are experienced by it namely,i. The gravitational force mg towards centre O.ii. The centrifugal force tryin... read more

Prove that gravitational potential difference is the work done in carrying a unit mass from one point to another. Answer: Gravitational potential at Gravitational Potential at Difference in potential ... read more

Consider a nearly circular orbit, prove that the square of time period of a planet is proportional to the cube of its radius. Answer: Consider a planet m moving around the sun (M) n an orbit of radius r. The centripetal force required is provided by ... read more

What are Geo – Stationary Satellite? Calculate the height of the orbit above the surface of the earth in which a satellite, if placed, will appear stationary. Answer: A satellite which revolves around the earth with the same angular speed in the same... read more

Briefly describe the Cavendish torsion balance. How is it used to measure G? Answer: It consists of two small lead balls (each of mass m) attached to the opposite ends of a light rod. This arrangement (with its axis horizontal) is suspended by a fine... read more

A comet orbits the sun in a highly elliptical orbit. Does the comet have a constant (a) Linear speed (b) Angular speed (c) Angular momentum (d) Kinetic Energy (e) Potential Energy (f) ... read more

A body is projected vertically upwards from the surface of the earth with an initial velocity v. Show that it will go up to height h given by . Answer: Let us consider a body of mass m with initial velocity v.Gravitational potential energy of th... read more

The masses and radii of the earth and the moon are M1, R1 and M2, R2 respectively. Their centres are a distance d apart. Find the minimum speed with which a particle of mass m should be projected from a point midway between the two centres ... read more

Find the ratio of the acceleration due to gravity of two planets (surface) if their radii are in the ratio 1:2 under the condition, i. Mass remains same. ii. Material remains same. Answer: i. if mass is same ... read more

The mass of the earth is 80 times that of the moon, while its radius is four times that of the moon. By what ratio will the weight of a body be reduced on the moon? Answer: The weight of an object of mass m on the surface of the earth is Where&n... read more

Discuss some properties of the motion of a freely falling body. Answer: 1) in vacuum, all bodies that start from rest, fall with same acceleration 2) in a given time, the velocity acquires by the body falling freely from rest is ... read more

Why can’t light come out of a black hole? Answer: If for some reason a celestial object begins to shrink, keeping its mass constant, then the escape velocity from that body begins to increase. If it becomes greater than or equal to the speed of light... read more

Write down four properties of geostationary satellites? Answer: 1) period of revolution is same as that of the earth’s spinning motion. 2) It moves from west to east with the orbiting velocity about 3.1km/s 3) The... read more

If a frictionless tunnel is bored along the diameter of the earth and a body is dropped in it, what will be the nature of its motion? Answer: The body will execute simple harmonic motion.... read more

What force keep the simple pendulum in simple harmonic
motion? Answer: The component of weight due to gravitational force ( i.e. keeps
the simple pendulum in simple harmonic motion.... read more

JEE-Main - Grade 12 - Physics - Electric Charges and Fields - Study ref# 10460

Check that the ratio is
dimensionless . Look up a table of physical constants and determine the value
of this ratio. What does the ratio signify? Answer: In the ratio (constant)
... read more

How are protons, which are positively charged,
held together inside a nucleus? Explain the variation of potential energy of
a pair of nucleons as a function of their separation. State the significance
of negative potential energy in this reg... read more