A 56-kg woman contestant on a reality television show is at rest at the south end of a horizontal 149-kg raft that is floating in crocodile-infested waters. She and the raft are initially at rest. She needs to jump from the raft to a platform that is several meters off the north end of the raft. She takes a running start. When she reaches the north end of the raft she is running at 4.2 m/s relative to the raft. At that instant, what is her velocity relative to the water

3.04 m/s

Explanation:

As the woman moves north, the raft moves south.

We then make the following assumptions for easier calculations

Let the motion of the woman = x

Let the motion of the raft = 4.2 - x

Using law of momentum, we see that

m*v = m1*v1, where

m = 56 kg

v = x

m1 = 149 kg

v1 = (4.2 -x)

Substituting the values into the equation, we have

56 * x = 149 (4.2 - x), opening the bracket

56x = 623 - 149x collecting like terms

205x = 623 Divide by 205

x = 623/205

x = 3.04 m/s

This then means that our answer is 3.04 m/s