Question

Car 1 was sitting at rest when it was hit from the rear by car 2 of identical mass. Both cars had their breaks on and they skidded together 6 m in the original direction of motion. If the stopping force is ~ 0.7  (combined weight of the cars) , i.e., combined weight of the cars) , i.e.,  = 0.7, find the approximate speed of car 2 just before the collision took place

Answer 1

Answer:

Sorry I don't know your answer you can search on

Answer 2

Answer: The speed of car 2 just before the collision took place was 12.83 m/s

Explanation:

Let the mass of both cars be m and the initial velocity of car 2 be u m/s.

Just after collision both cars move with speed v m/s.

There is no external force on cars during collision, hence momentum can be conserved during collision.

Momentum just before collision = Momentum just after coliision

                    mu + 0                     =    2mv

                      u/2                        =     v

After collision , cars skid for 6m.

$v^{2} - u^{2} = 2as$

$0 - \frac{u^{2} }{4} = 2a(6)$

$a = - \frac{u^{2} }{24}$

Net resisting force = 2m × u²/24

       0.7 × 2mg       =   mu²/12

       u²   =  0.7 × 2 × 12 × g

         u²   = 0.7  × 2  × 12  × 9.8

        u²  = 164.64

        u  =  12.83

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