In an Elastic Collision Between Two Bodies of Mass M₁

Multiple Choice

In an elastic collision between two bodies of mass m₁ and m₂, with m₂ initially at rest, mass 1 moves off at angle θ relative to the direction of its initial velocity and mass 2 at angle φ. An exam paper shows the equations below: m₁v_1i
0
= m₁v_1f cosθ + m₂v_2f sinφ
= m₁v_1f sinθ + m₂v_2f cosφ
What error(s) has the student made?

A) In the first equation, m₂v_2f sinφ should be m₂v_2f cosφ.
B) In the second equation, m₂v_2f cosφ should be m₂v_2f sinφ.
C) In the second equation, the plus sign between the terms on the right should be a minus sign.
D) All of the errors listed above.
E) Only errors (a) and (b) above.