In a car crash, Car A rear ends Car B that stopped at a red light. After the cra
ID: 1472583 • Letter: I
Question
In a car crash, Car A rear ends Car B that stopped at a red light. After the crash, Car A and Car B meld together moving at a speed of 14 m/s. Car A has a mass of 1750 kg. Car B has a mass of 2000 kg. (Please show work)
What is the name of this type of collision?
Calculate the momentum after the crash.
Calculate the initial momentum of Car A.
Calculate the initial momentum of Car B.
Calculate the initial speed of Car A.
Suppose the speed limit for the road is 60 mph = 26.8 m/s was Car A speeding?
Calculate the initial kinetic energy of Car A.
Calculate the initial kinetic energy of Car B.
Calculate the final kinetic energy of Cars A & B melded together.
Explanation / Answer
1) This type is called perfectly Inelastic collision
2) momentum after crash = ( mA + mB )× v
= (1750+ 2000) × 14 = 52500 kg.m/s
3)Initial momentum of car A = 52500 kg.m/s ( Initial momentum of car B was zero )
4) Initial momentum of car B = 0 ( initial velocity = 0 )
5) Initial speed of car A = momentum / mass
= 52500/ 1750 = 30 m/s
Yes it was speeding (exceeds 26.8 )
6) Initial kinetic energy ( Ke) of car A = m v^2 / 2
= 1750× 30^2 / 2 = 7.875*10^5 J
7) Initial (Ke) of car B = 2000× 0^2/2 = 0
8) Final (Ke) = 3750 × 14^2 /2 = 3.675*10^5 J