A3.0-kg object moves to the right at 4.0 m/s. it collides head-on with a 6.0-kg object moving to the left at 2.0 m/s.

which statement is correct?
a) the total momentum both before and after the collision is zero.
b) the total momentum both before and after the collision is 24 kg·m/s.
c) the total momentum before the collision is 24 kg·m/s, and after the collision is 0 kg·m/s.
d) none of the above is true.

A

Explanation:

momentum is a vector quantity and if velocity is towards right it is positive and if velocity is  towards left it is negative . Also momentum is product of mass and velocity .

hence initial momentum  = 3×4 +6 × -2

                                        = 12 -12

                                         = 0

according to law of conservation of momentum , momentum after collision must be zero . Hence  A is the answer

b.a device that inputs heat into a cool object