Most of the skid mearks left at the scence of an automobile accident are left by the car tires after the collision occurs. How can measuring the direction and length of these skid marks. After the collision reveal whether either of the cars involved was speeding before the collision?

In the "before" part of Fig., car A (mass 1100 kg) is stopped at a traffic light when it is rear-ended by car B (mass 1400 kg). Both cars then slide with locked wheels until the frictional force from the slick road (with a low mu_k of 0.10) stops them, at distances d_A = 8.2 m and d_B = 6.1 m. What are the speeds of (a) car A and (b) car B at the start of the sliding, just after the collision? (c) Assuming that linear momentum is conserved during the collision, find the speed of car B just before the collision. (d) Explain why this assumption may be invalid.

According to a FIR in police station, car A was at rest waiting for a red light at a crossing when it was hit by similar car B from rear side. Both cars had then hard brekes on, and from their skid marks it is surmiesed that they skidded together about 8m in the original direction of travel before coming to rest. Assuming a stopping force of about 0.4 times the combined weights of the cars. the speed of car B just before the collision is approximately [g=10 m//s^(2)]

Collision is a physical process in which two or more objects, either particle masses or rigid bodies, experience very high force of interaction for a very small duration. It is not essential for the objects to physically touch each other for collision to occur. Irrespective of the nature of interactive force and the nature of colliding bodies, Newton's second law holds good on the system. Hence, momentum of the system before and after the collision remains conserved if no appreciable external force acts on the system during collision. The amount of energy loss during collision, if at all, is indeed dependent on the nature of colliding objects. The energy loss is observed to be maximum when objects stick together after collision. The terminology is to define collision as 'elastic' if no energy loss takes place and to define collision as 'plastic' for maximum energy loss. The behaviour of system after collision depends on the position of colliding objects as well. A unidirectional motion of colliding objects before collision can turn into two dimensional after collision if the line joining the centre of mass of the two colliding objects is not parallel to the direction of velocity of each particle before collision. Such type of collision is referred to as oblique collision which may be either two or three dimensional. A 4 kg sphere moving with a velocity of 4 m//s collides with an identical sphere of 2 kg moving with 2 m//s as shown. Final kinetic energy is less than initial kinetic energy. What type of collision is this?