A railroad car of mass m and speed v collides and sticks to an ...

[casperchen82]

A railroad car of mass m and speed v collides and sticks to an identical railroad car that is initially at rest. After the collision, the kinetic energy of the system
 
  A) is the same as before.
  B) is half as much as before.
  C) is one third as much as before.
  D) is one fourth as much as before.
  E) is one quarter as much as before.

Question 2

The angular velocity of a 755-g wheel 15.0 cm in diameter is given by the equation
 
  (t) = (2.00 rad/s2 )t + (1.00 rad/s4 )t3.
  (a) Through how many radians does the wheel turn during the first 2.00 s of its motion?
  (b) What is the angular acceleration (in rad/s2 ) of the wheel at the end of the first 2.00 s of its motion?

[morrie123456]

Answer to Question 1

B

Answer to Question 2

(a) 8.00 rad (b) 14.0 rad/s2

[casperchen82]

Wow, this really help

[xiaomengxian]

Excellent