Answer:
0.7 m/s
Explanation:
We can solve the problem by using conservation of momentum.
Before the collision, the momentum of the first tackler is:
while the momentum of the second tackler is
Note that we used a negative sign because the direction of the second tackler is opposite to that of the first tackler.
Therefore, the total momentum before the collision is
Since the total momentum is conserved, this is also equal to the final total momentum :
Which is also equal to
since the two tacklers continue their motion together with final velocity vf. Re-arranging the previous equation, we can find the the new velocity of the two tacklers:
and the negative sign means the direction is the one of the second tackler.