a blue honda civic rear-ends a parked and identical, but red, Honda civic. Use m=1000 kg. The speed of the blue honda right before collision is 20 m/s (45 mph) to the right.
A) If the speed of the red honda after the colision was 12 m/s, what is the speed of the blue Honda right after the colision?
B) How much impulse is delivered to the red honda by the blue honda? How much impulse is delivered to the blue honda by the red honda?
C) If the colision lasted 12 ms (that is 12 milliseconds), what was the average force acting on the blue honda and red honda?
D) If red honda installed an ideal spring of (K=800,000 N/m) on the rear bumper of his car (which prevents any damage to occur to the other cars durring this collision), what is the speed of the two cars right after the colision?
A) The momentum of the system is conserved as there is no external force on the two cars.
Initial momentum of the two cars = final momentum of the two cars
1000 x 20 + 1000 x 0 = 1000 x v + 1000 x 12
20 = v +12 => v = 8 m/s
The speed of the blue honda after collision is 8 m/s.
B) The impulse is change in momentum = final momentum - initial momentum
The impulse delivered to red honda = 1000 x 12 - 1000 x 0 = 12000 N-s
The impulse delivered to blue honda = 1000 x 8 - 1000 x 20 = - 12000 N-s
C) The average force = change in momentum / time = 12000 / 0.012 = 106 N
D) If there is no damage to the cars then the collision is said to be elastic collision. In this collision, momentum is conserved and kinetic energy is also conserved. Otherwise, the relative velocity of approach is equal to relative velocity of separation.
Let u1 = 20 m/s and u2 =0 be the initial speeds. Let v1 and v2 be the final speeds.
1000 u1 + 1000 u2 = 1000 v1 + 1000 v2 => 20 = v1 + v2 _____________1
relative velocity of approach = relative velocity of separation
u1 - u2 = v2 - v1 => v2 - v1 = 20 _______________2
Adding the two equations, 2 v2 = 40 => v2 = 20 m/s then v1 = 0
The blue honda comes to rest and red honda moves with 20 m/s after collision.
a blue honda civic rear-ends a parked and identical, but red, Honda civic. Use m=1000 kg....