On a bus traveling north at 20.0ms child stands up and walks to the back of 1.3ms What is resultant velocity?

To find the resultant velocity of the child, we need to first determine the velocity of the child relative to the bus and then add that to the velocity of the bus.

The velocity of the child relative to the bus is:

$$v_{child/bus} = -1.3\text{ m/s}$$

where the negative sign indicates that the child is walking towards the back of the bus (opposite direction of bus's motion).

The velocity of the bus is:

$$v_{bus} = 20\text{ m/s}$$

The resultant velocity of the child is:

$$v_{child} = v_{child/bus} + v_{bus}$$

$$v_{child} = -1.3\text{ m/s} + 20\text{ m/s}$$

$$v_{child} = 18.7\text{ m/s}$$

Therefore, the resultant velocity of the child is 18.7 m/s in the same direction as the bus.