[1] At relativistic speeds near that of light, A) an object is longer when movin

ID: 1641121 • Letter: #

Question

[1] At relativistic speeds near that of light,

A) an object is longer when moving than when it is stationary.

B) the half-life of an unstable particle moving at high speed is longer than when it is at rest.

C) light emitted by a moving source moves at the same speed with the same frequency.

D) lengths and times only appear different, the y are really just the same.

E) effects precede causes in some inertial frames.

[2] In relativistic particle collisions or decays,

A) momentum and energy are still conserved.

B) momentum and energy are conserved from frame to frame.

C) the mass of a particle is different for various observers.

D) the energy equals the sum of the momentum, pc, plus the mass, mc2.

E) only energy is conserved.

[3] Particles with mass are prevented from moving at the speed of light by

A) the shock wave or “light boom” that builds up as light waves bunch up.

B) the increasing cost in energy as they approach the speed of light.

C) the laws of relativity enforced by the physics police.

D) the contraction of their length to zero.

E) time slowing to a stop.

[4] A mixture of two gases is kept at a uniform temperature. The particles in the mixture

a) all have the same speed.

b) all have the same average speed.

c) have a higher average speed for the lighter mass particles.

d) have a lower average kinetic energy for the more massive particles.

(1) Option (d) is correct.

Explanation:

Object length shall be shorter, as the expression is given by -

L = L0 * sqrt[1 - v^2 / c^2]

So, length and time shall be different.

(2) Option (A) is correct.

Momentum and energy shall always be conserved for all type of collision.

(3) Option (B) is the correct answer.

As the speed of a object increses, its mass also increases. As the speed reaches to light speed, its mass becomes infinity which is impossible.

(4) Option (b) is the correct option.

Average speed depends on the temperature. So, they have the same average speed.

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