A proton, of mass m and speed v, strikes an alpha-particle (which ...

[NClaborn]

A proton, of mass m and speed v, strikes an alpha-particle (which consists of 2 protons and 2 neutrons) at rest.
 
  If the collision is completely elastic, what speed will the -particle have after the collision? (Assume the neutron's mass equals the proton's mass.) A) zero
  B) 3/2 v
  C) 2/5 v
  D) 2/3 v
  E) 5/3 v

Question 2

Which is NOT a critical factor that determines the habitability of a rocky planet?
 
  A) size
  B) distance from parent star
  C) presence of a magnetic field
  D) presence of an atmosphere

[SomethingSomething]

Answer to Question 1

C

Answer to Question 2

C

[NClaborn]

Thanks for the timely response, appreciate it

[bdobbins]

Wow, this really help