need all steps please Name: ENGR 2334 Exam 1, Spring 2017 Bonus (+10). You have

Question

need all steps please

Name: ENGR 2334 Exam 1, Spring 2017 Bonus (+10). You have an excellent idea to improve the safety of cars. Instead of plastic bumpers, you want to put springs on the front so that they can absorb the energy of impact during a car crash. Your car weighs 2,000 kg. You replace vour front bumper with springs that have a spring constant of 5 kN/m and an initial length of 15 cm. The shortest that the spring can get without being damaged is 10 cm. b. How much energy must your spring system absorb if your car hits a wall traveling at a velocity of 30 m/s (about 70 mph)? c. How many springs would it take to absorb this much energy? Why do you think car companies do not employ this safety method?

Explanation / Answer

Given weight of car = 2000 kg , spring constant = 5000 N/m ,

spring initial length = 15 cm,spring shortest length without damage = 10 cm

b) if car of mass 2000 kg travelling with a speed of 30 m/s hits a wall ,

since car comes to rest after hitting a wall,the spring system should absord the kinectic energy of car

so,energy which should be absorbed by spring system = 0.5*2000*30*30 = 900 kJ

c) since shortest lenght by which a spring can go is 10 cm ,

maximum compression allowed in spring = 15-10 = 5cm = 0.05 m

maximum energy a spring can absorb = 0.5*K*x2 = 0.5*5000*0.05*0.05 = 6.25 J

no of springs reuired to absorb energy = 900000/6.25 = 144000

why car companies wont consider spring system means i can say two reasons

1.from above result we need 144000 springs to abosrb energy which makes system comlicated for service

2.springs after absorbing energy by compression it will bounce back thereby it will cause harm to people in car

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