(a) What is the speed of car A at thestart of the sliding? 1 m/s (b) What is the

Question

(a) What is the speed of car A at thestart of the sliding?
1 m/s

(b) What is the speed of car B at the start of thesliding?
2 m/s

(c) Assuming that linear momentum is conserved during thecollision, find the speed of car B just before thecollision.
3 m/s

(d) Explain why this assumption may be invalid.
4 In the before part of the figure below, car A (mass1000 kg) is stopped at a traffic light when it is rear-ended by car B (mass 1500 kg). Both cars then slide with locked wheels until the frictional force from the slick road (with a low muk of 0.12)stops them, at distances dA = 8.2 m anddB = 6.1 m. (a) What is the speed of car A at the start of the sliding? 1 m/s (b) What is the speed of car B at the start of the sliding? 2 m/s (c) Assuming that linear momentum is conserved during the collision, find the speed of car B just before the collision. 3 m/s (d) Explain why this assumption may be invalid. 4

Explanation / Answer

(a)the speed of car A at the start of the sliding v1^2 - u1^2 = 2kgS1 or u1 = -(2kgS1)^(1/2) -----------(1) the negative value of speed indicates that the car A issliding against the frictional force. v1 = 0,k= 0.12,g = 9.8 m/s^2 and S1 =dA= 8.2 m (b)the speed of car B at the start of the sliding v2^2 - u2^2 = 2kgS2 or u2 = -(2kgS2)^(1/2) ------------(2) v2 = 0 and S2 = dB= 6.1 m (c)when the linear momentum is conserved during the collisionthen m1 * u1 + m2 * u2 = m1 * v1 + m2 * v2 m1 = 1000 kg,u1 = 0,m2 = 1500 kg,u2 = vo,the valueof u1 is obtained from equation (1) and the value of v2 is obtainedfrom equation (2) (d)This assumption may not be valid.This is because when thelinear momentum is conserved then the two cars must have the samevelocity after the collision as they stick together.The linearmomentum is conserved in a inelastic collision in which the twoobjects stick together after the collision.

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