For an experiment to produce useful data, what must happen? A. It must be performed

D

Explanation: It must be repeated several times. (You could have different results everytime. Kind of like a dice. If you only roll it once and get a 3, you will only think it rolls a 3 unless you roll it and get different results or unless you've seen a dice before.)

0.2 km/m east

Explanation:

The magnitude of Walt's velocity is given by:

where

s is Walt's displacement

t is the time taken

In this problem, Walt's displacement is s=5 km, while the time taken is t=25 m, so the velocity is

and the direction is east, since Walt is running eastwards.