Question

If a hockey player starts from rest and accelerates at a rate of 2.1 m/s2, how long does it take him to skate 30

Answer 1

I'll assume you meant to say 30 meters.

Let's see what we have...
\[a=2.1 \ m/s^2\]\[v_\text{initial}=0 \ m/s \ (\text{started from rest...})\]\[x_\text{initial}=0\]\[x_{final}=30 \ m\]\[t = \text{unknown}\]

Which kinematic equation can we use to solve for t?