Posted by **sam** on Friday, September 14, 2012 at 11:09pm.

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.

- physics -
**sam**, Friday, September 14, 2012 at 11:14pm
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.

- physics -
**drwls**, Saturday, September 15, 2012 at 1:06am
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.

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