Question

Q2 Car bumpers are designed to limit the extent of damage to the car in the case of low-velocity collisions. Consider a 1420 kg passenger car impacting a concrete barrier while traveling at a speed of 5.0 km/h. Model the car as a particle and consider two bumper models: (1) a simple linear spring with constant k and (2) a linear spring of constant k in parallel with a shock absorbing unit generating a nearly constant force Fs = 2000 N over 10 cm. Problem 4.231 If the bumper is of type (1) and if k = 9x 104 N/m, find the spring compression (distance) necessary to stop the car. LE

Answer 1

On applying conservation of energy that is loss in kinetic energy= Gain in spring potential energy

Therefore

where x is the compression of spring in meteres.

Given v==

K=

9 * 10+N/m

m=

we get $x=0.03m=30mm$

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