Speed calculation based on projectile motion

5 Nov by Iskandar Abdul Hamid

Speed calculation based on projectile motion

Data:

Bus height, hbus = 3.743m

CG height =hCG = 3.743/3 = 1.248m

CG tilt, htilt = 2.60/2 = 1.30m.

Guardrail height, hG = 1.05m

Change in CG height,

h = hG + htilt – hCG = 1.102m

d = 10.52m

 

The angle that will give the minimum speed is calculated using equation

“θ”=1/2  cos^(-1)⁡[(-h)/√(d^2- h^2 )]*

Velocity of a vehicle at the point of take off is

v=d√(g/(2cos”θ” (dsin”θ” -hcos”θ” )))*

 

From the data and formula used, calculated angle,

“θ” = 48°. This gives the minimum speed of the bus at the point of take off as V = 38.5 km/hr.

However, if the angle is taken from the site measurement which is “θ” = 34.1°, the calculated speed is V = 41.2 km/hr.

Therefore, the possible speed of the bus at the point of take off is 41.2 km/hr.

 

*Ref: Lynn B Fricke, ‘Traffic Crash Reconstruction’, Northwestern University, Centre for Public Safety, Evanston, Illinois, 2010.

Leave a Reply

Your email address will not be published. Required fields are marked *