Which of the Following Are Required for the Total Momentum

Multiple Choice

Which of the following are required for the total momentum (both angular and linear) of a system to be conserved?
1.The sum of the external torques acting on the system must be zero.
2.The sum of the external forces acting on the system must be zero.
3.The total kinetic energy must remain constant.
4.There can be no external torques or forces acting on the system.
5.There can be no internal torques or forces acting on the system.

A) 1 and 2
B) 1, 2, and 3
C) 1, 2, and 4
D) 1, 2, 3, and 4
E) 1, 2, 3, 4, and 5