The velocity of the girl is -4.8 m/s.
Using the principle of conservation of linear momentum, The total momentum of bodies before and after collision is constant. Since the two objects are stationary, the initial momentum of each body is zero.
Thus;
0 = (80 × 3) + (50 × v)
0 = 240 + 50 v
-240 = 50 v
v = -240/50
v = -4.8 m/s
Note that the negative sign shows that the velocity of the girl is in opposite direction that that of the girl.
Learn more about momentum: brainly.com/question/904448
Answer:

Explanation:
Given data

To find
Mutual inductance of the two-coil system
Solution
The mutual inductance given as:
M= (-VΔt)/ΔI
Substitute the given values
So

Period = (1/frequency) .
If frequency is 100 per second, then
Period = (1) / (100 per second) = 0.01 second .
Speed is the same as the initial: 25m/s.
*if* you need vectors though:
final velocity = (25*cos(35), -25*sin(35) ) m/s