Question 1

Explain why it is impossible for an object to travel at the speed of light.

Accepted Answer

The answer of Explain why it is impossible for an...

Question 2

Astronauts travel to a star 2000 light-years from Earth in a spaceship capable of speeds approaching,but not exceeding,the speed of light.Is it possible that the original astronauts will still be alive when the spaceship reaches the star? Why or why not?

Accepted Answer

The answer of Astronauts travel to a star 2000 light-years...

Question 3

An object of mass M is initially moving at a speed of 0.999 c and collides inelastically (they stick)with another identical object that was initially at rest.After the collision,the two objects are moving with a speed

Accepted Answer

The answer of An object of mass M is initially...

Question 4

A star is moving toward Earth with a speed of 0.9 c (90% the speed of light).It emits light,which moves away from the star at the speed of light.Relative to us on Earth,the speed of the light moving toward us (emitted by the star)is

Accepted Answer

According to the theory of relativity, the speed of light in a vacuum is always constant at c, regardless of the motion of the source or the observer.

Question 5

The kinetic energy of an object moving at 10% the speed of light is

Accepted Answer

At 10% the speed of light, relativistic effects start to become significant, making the kinetic energy slightly higher than the classical (1/2)mv^2.

Question 6

A person buys a SUV and discovers that it is too long to fit in the garage (the length of the SUV is 1.3 times the length of the garage).He decides to drive the SUV into the garage at a speed of 0.99 c.Which statement is true?

Accepted Answer

According to the theory of relativity, a person standing near the garage will see the SUV length contracted and fitting inside the garage, while the driver will not see it entirely inside due to relativistic effects.

Question 7

A light source is flashing on and off with a frequency of 1 Hz.If you were to run really fast (say 80% the speed of light),with your direction of motion perpendicular to the direction of the light,you would observe the frequency of the flashing to

Accepted Answer

The answer of A light source is flashing on and...

Question 8

A spaceship is moving in a straight line at a speed of 0.8 c (relative to Earth).It launches a missile that moves away from the spaceship (traveling in the same direction as the spaceship)at a speed of 0.6 c.Relative to Earth,the speed of the missile is

Accepted Answer

The velocity addition formula gives the relative velocity of the missile with respect to Earth as: 
v_m = (v_s + v_r) / (1 + v_s*v_r/c^2), 
where v_s = 0.8c is the velocity of the spaceship and v_r = 0.6c is the velocity of the missile relative to the spaceship. 
Plugging in the values, we get: 
v_m = (0.8c + 0.6c) / (1 + 0.8c*0.6c/c^2) = 1.4c/(1+0.48) = 0.944c. 
Therefore, the correct choice is A as the missile moves away from the spaceship at a speed that is greater than 0.8c (velocity of the spaceship relative to Earth) but less than c (speed of light in vacuum).

Quiz 27: Relativity

Explain why it is impossible for an object to travel at the speed of light.

Astronauts travel to a star 2000 light-years from Earth in a spaceship capable of speeds approaching,but not exceeding,the speed of light.Is it possible that the original astronauts will still be alive when the spaceship reaches the star? Why or why not?

An object of mass M is initially moving at a speed of 0.999 c and collides inelastically (they stick) with another identical object that was initially at rest.After the collision,the two objects are moving with a speed

A star is moving toward Earth with a speed of 0.9 c (90% the speed of light) .It emits light,which moves away from the star at the speed of light.Relative to us on Earth,the speed of the light moving toward us (emitted by the star) is

The kinetic energy of an object moving at 10% the speed of light is

A person buys a SUV and discovers that it is too long to fit in the garage (the length of the SUV is 1.3 times the length of the garage) .He decides to drive the SUV into the garage at a speed of 0.99 c.Which statement is true?

A light source is flashing on and off with a frequency of 1 Hz.If you were to run really fast (say 80% the speed of light) ,with your direction of motion perpendicular to the direction of the light,you would observe the frequency of the flashing to

A spaceship is moving in a straight line at a speed of 0.8 c (relative to Earth) .It launches a missile that moves away from the spaceship (traveling in the same direction as the spaceship) at a speed of 0.6 c.Relative to Earth,the speed of the missile is