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IET » Student and apprentice discussion forum » Calculation check Topic Title: Calculation check
Topic Summary: Deceleration
Created On: 18 October 2009 06:11 PM
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18 October 2009 06:11 PM
BK
Posts: 11
Joined: 28 September 2009
Can anyone give this the once over make sure I have the formula calcs etc right
Vehicle mass 5 Tonnes traveling with a velocity 80kmh. It needs to stop with in 0.5km using constant braking force
Deceleration:
(80kmh = 80x1000/3600 = 22.2m/s)
a=(v^2-u^2) / 2s
a=(0-22.2^2)/2x500
a=(493.83)/1000
a= 0.494ms
as Deceleration = -0.49
Just want to check I am on the right line
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19 October 2009 01:45 PM
tonysung
Posts: 579
Joined: 14 September 2001
It's a very good start. Perhaps you could add a few explanatory notes to your working so it can be checked properly.
E.g., "Deceleration80kmh = 80x1000/3600 = 22.2m/s)" should be 'velocity' or 'speed' in m/s.
Please have another go.
Kind regards
-------------------------
tony sung
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19 October 2009 07:11 PM
BK
Posts: 11
Joined: 28 September 2009
Apologies that should have been Velocity 22.2ms
My concern is whilst working out time taken
V/A=T, 22.2/0.4938 = 45s
I checked using a Velocity, Time distance calculator on the net and it calculates 22.5s
Therefore was I correct in using 2s in my initial calculation, it appears to be correct when I transformed the formula