Home
Class 12
PHYSICS
The radius of our galaxy is about 3 xx 1...

The radius of our galaxy is about `3 xx 10 ^(20)m`.With what speed should a person travel so that he can reach from the centre of the galaxy to its edge in 20 years of his lifetime ?

Text Solution

Verified by Experts

Let the speed of the person be v . As seen by the person, the edge of the galaxy is coming towards him at a speed v. In 20 years (as measured by the person ), the edge moves (20 y ) v and reaches the person. The radisu of the galaxy as measured by the person is , therefore , (20 y)v . The rest length of the radius of the galaxy is ` 3 xx 10^(20)m. ` Thus ,
` (20y )v = (3 xx 10^(20)m) (sqrt 1 - v ^(2)/ c^(2) `
or, (6 .312 xx 10 ^(8) s ) ^(2) v^(2) = (9 xx 10 ^(40) m ^(2)) (1- v^(2) / c^(2) )`.
Solving this,
v =0.9999996 c.
Promotional Banner

Topper's Solved these Questions

  • THE SPECIAL THEORY OF RELATIVITY

    HC VERMA|Exercise Short answer|5 Videos

  • THE SPECIAL THEORY OF RELATIVITY

    HC VERMA|Exercise Objective|7 Videos

  • THE SPECIAL THEORY OF RELATIVITY

    HC VERMA|Exercise Exercise|28 Videos

  • THE NUCLEOUS

    HC VERMA|Exercise Exercise|53 Videos

  • THERMAL AND CHEMICAL EFFECT OF ELECTRIC CURRENT

    HC VERMA|Exercise Exercise|24 Videos

Similar Questions

Explore conceptually related problems

A boy is standing on a platform which is free to rotate about its axis. the boys holds an open umbrella in his hand. The axis of the umbrella coincides with tht of the platform. The moment of inertias of the platform plus the boy sytem is 3.0xx10^-3 kg-m^ and that of the umbrella is 2.0xx10^-3 kg-m^2 . The boy starts spinning the umbrella about the axis at an angular speed of 2 rev s1 with respect to himself . Find the angular velocity imparted to the platform.

An electric field of magnitude 1000 NC ^(-1) is produced between two parallel platees having a separation of 2.0 cm as shown in figure(29.E4) (a) What is the potential difference between the plates? (b) With what minimum speed should an electron be projected from the lower plate in the direction of the field so that it may reach the upper plate? ( c) Suupose the electron is projected from the lower plate with the speed calculated in part (b) . The direction of projection makes an angle of 60@ with the field. Find the mazimum height reached by the electron.

A circular coil of 200 turns has a radius of 10 cm and carries a current of 2.0 A. (a) Find the magnitude of the magnetic field (vec B) at the centre of the coil. (b) At what distance from the centre along the axis of the coil will the field B drop to half its value at the centre?

A 100 turn closely wound circular coil of radius 10 cm carries a current of 3.2 A. a. What is the field at the centre of the coil ? b. What is the magnetic moment of this coil ? The coil is placed in a vertical plane and is free to rotate about a horizontal axis which coincides with its diameter. A unifrom magnetic field of 2 T in the horizontal direction exists such that initially the axis of the coil is in the direction of the field. The coil rotates through an angle of 90^@ under the influence of the magnetic field . c. What are the magnitudes of the torques on the coil in the initial and final position ? d. What is the angular speed acqired by the coil when it has rotated by 90^(@) ? The moment of inertia of the coil is 0.1 kg m^2

A solid cylinder of mass 20 kg rotates about its axis with angular speed 100 rad/s. The radius of the cylinder is 0.25 m. What is the kinetic energy associated with the rotation of the cylinder ? What is the magnitude of angular momentum of the cylinder about its axis ?

A car of mass 1500 kg is moving with a speed of 12.5 ms^(-1) on a circular path of radius 20 m on a level raod what should be the frictional force between the car and the raod so that the car does not slip what should be the value of the coefficent of friction to attain this force

A steel wire has a length of 12.0m and a mass of 2.10kg. What should be the tension in the wire so that speed of a transverse wave on the wire equals the speed of sound in dry air at 20^(@)C= 343ms^(-1)

A straight horizontal wire of mass 10mg and length 1.0 m carries a current of 2.0 A. what minimum magnetic field B should be applied in the region so that the magnetic force on the wire may balance its weight?