physics
posted by sam .
An airport has runways only 136m long. A small plane must reach a ground speed of 39m/s before it can become airborne.
What average acceleration must the plane's engines provide if it is to take off safely from its airport?
Answer in units of m/s^2.

Highway safety engineers build soft barriers so that cars hitting them will slow down at a soft rate. A person wearing a safety belt can withstand an acceleration of 300m/s^2.
How thick should barriers be to safely stop a car that hits the barriers at 92.8km/h?
Answer in units of m. 
V = sqrt(2 a X)
V is the speed that must be attained
a is the acceleration
X is the distance required
Solve for a.