The half life of a π - meson at rest is 1 . 8 × 10 - 8 seconds . What will be its half life when it will travel with the speed of c / 2 ?

Applying time dilation concept, Let T 1 2 be half life when it travels with speed v = c 2 . T 1 2 = t 1 2 1 - v 2 c 2 ⇒ T 1 2 = 1 . 8 × 10 - 8 1 - c 2 2 c 2 ⇒ T 1 2 = 1 . 8 × 10 - 8 1 - 1 4 ⇒ T 1 2 = 2 . 8 × 10 - 8 seconds

E M B I B E

Bureau's Higher Secondary Physics Class 12>Chapter 15 - Relativity>MODEL QUESTIONS>Q 8

MEDIUM

12th Odisha Board

IMPORTANT

Earn 100

An electron is chased by a proton. The speed of the electron is $0.9 c$ . Show that their relative velocity is $c$ . (Where $c$ is speed of light in vacuum).

Important Questions on Relativity

EASY

12th Odisha Board

IMPORTANT

Bureau's Higher Secondary Physics Class 12>Chapter 15 - Relativity>MODEL QUESTIONS>Q 9

A young fat girl dances with high velocity. Explain why she will appear less fat to her stationary friends.

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12th Odisha Board

IMPORTANT

Bureau's Higher Secondary Physics Class 12>Chapter 15 - Relativity>MODEL QUESTIONS>Q 10

What is meant by the total energy of a body in special theory of relativity?

HARD

12th Odisha Board

IMPORTANT

Bureau's Higher Secondary Physics Class 12>Chapter 15 - Relativity>MODEL QUESTIONS>Q 1

A rocket is $100 m$ long on the ground. If its length decreases by $1 m$ to an observer on the ground during its flight, calculate the speed of length.

HARD

12th Odisha Board

IMPORTANT

Bureau's Higher Secondary Physics Class 12>Chapter 15 - Relativity>MODEL QUESTIONS>Q 2

How much younger an astronaut will appear to earth if he returns after one year having move with velocity equal to $0.5 C$ ?

HARD

12th Odisha Board

IMPORTANT

Bureau's Higher Secondary Physics Class 12>Chapter 15 - Relativity>MODEL QUESTIONS>Q 3

Two electrons are moving in opposite directions with velocity

0.6 c

and

0.7 c

as measured by laboratory observer. What is the velocity of one electron with respect to other electron? (Where

c

is speed of light in vacuum)

EASY

12th Odisha Board

IMPORTANT

Bureau's Higher Secondary Physics Class 12>Chapter 15 - Relativity>MODEL QUESTIONS>Q 4

The half life of a

π - meson

at rest is

1.8 \times 10^{- 8} seconds .

What will be its half life when it will travel with the speed of

c / 2

?

MEDIUM

12th Odisha Board

IMPORTANT

Bureau's Higher Secondary Physics Class 12>Chapter 15 - Relativity>MODEL QUESTIONS>Q 5

How much energy will be released from annihilation of

1 k g

of matter?

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12th Odisha Board

IMPORTANT

Bureau's Higher Secondary Physics Class 12>Chapter 15 - Relativity>MODEL QUESTIONS>Q 6

A spaceship is launched from earth surface with a velocity of

0.3 c

. It fires a rocket with a velocity of

0.6 c

relative to spaceship away from the earth. What will be the velocity of rocket observe from Earth’s surface? In the above case, calculate the velocity as observed from the rocket surface.