henripoincare
13th October 2008 - 09:16 PM
1. The problem statement, all variables and given/known data
Take off speed of jet: 278km/hours
Aircraft-Carrier catapult distance: 94m (distance)
Assume constant acceleration.
How long will it accelerate?
2. Relevant equations
s = .5at^2
v = at
3. The attempt at a solution
1) Conversion to m/sec: (278*1000)/60 = 4633.3
s = .5 (v)*t
t = 2(s)/v
t = (2*94)/4633.3
t = 0.04058
=================================
Correct Solution: It will accelerate for 2.43 seconds.
bm1957
14th October 2008 - 07:54 AM
You've converted to m/min. You need to divide by 60 again to get m/sec
Your second equation isn't complete, it should read:
v = u + at
Your method will work, since u=0, but I would suggest using the equation:
s = 0.5(u+v)t;
t = 2s/(u+v); (u=0)
t = 2s/v; (we are back to the equation you found, but if u wasn't 0, you would have hit problems your way)
With a new value for the velocity (m/sec), you should be able to get the correct answer.
Hope that helps!