diff --git a/education/physics/PHYS2210/Unit 1.md b/education/physics/PHYS2210/Unit 1.md
index b021e83..f1a884e 100644
--- a/education/physics/PHYS2210/Unit 1.md	
+++ b/education/physics/PHYS2210/Unit 1.md	
@@ -57,4 +57,11 @@ Kinematics problems have a *start* and an *end* of the motion.
 1. The problem is a kinematics problem, refer to the above formula.
 2. Acceleration is a constant
 3. Problem has two unknowns, $v_0$ and $a$, let's solve for $v_0$ first.
-4. 
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+4. $x = x_0 + \frac{1}{2}(v_0 + v) t \to v_0 = 2*(x - x_0)/ t \to 2*(15)/3 = 10$
+5. $v = v_0 + at \to a = (v - v_0) /t \to a = (-10 m/s) / 3s = -3.33m/s^2$ 
+6. Asses: Units? Answer make sense? Significant figures? Acceleration speeding up or slowing down?
+# Gravity
+- Is the problem 1 dimensional?
+- Could draw axis pointing upwards, call it y axis
+- If not specified, assume acceleration is $g = 9.8 m/s^2$.
+- Direction is important, $g$ is down towards the earth, so it's often negative. The sign depends on your choice of axis. 
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