Car Crash Car crash (traffic collision) causes injury, damage or even death. It occurs when a moving motor vehicle collides with either another moving object or a stationary object. The risk of a traffic collision occurring is determined by the following factors which also influence the physics of a car crash: vehicle design, road design, driving skills of the driver, speed of the motor vehicle before impact, road environment, level of psychological impairment (caused by alcohol consumption or substance abuse) and behavioral disposition like street racing and speeding (Bartley, 2008). Physics of a Car Crash The physics of collision describe the process and outcome of a car crash. As stated earlier, the motor vehicle before crashing was in motion. Newton’s laws of motion do aid in understanding the physics of traffic collision. Laws of Motion Newton’s first law of motion states that a stationary object remains stationary if no external force is applied to the object. It also states that a moving object would remain in motion at a constant velocity if no external force is applied to it (Field, 2015). Therefore, a stationary object on the road would remain stationary if no external force is applied. Also, a moving car would travel in constant velocity if no external force is applied. Newton’s second law of motion deals with objects in motion. It states that the rate of acceleration is directly proportional to the combined net force involved and also inversely CAR CRASH 3 proportional to the mass of the object (Field, 2015). Thus, it can be deduced that force is the product of mass and the rate of acceleration. Newton’s third law of motion deals with collision. It states that when two objects, A and B, collide; the force that is exerted by object A onto object B is of equal magnitude but in opposite direction to the force exerted by Object B onto Object A (Field, 2015). Thus, an action has an equal reaction albeit in opposite direction. Kinetic and Static Friction Another important concept in traffic collision is friction. Friction is the force which resists motion when two objects contact each other. Different materials have different levels of friction, thus, each material has its coefficient of friction. For motion to occur when Object A is resting on the ground, the applied force must be greater than the normal force of Object A and the force of friction. Static friction keeps two objects from moving away from each other, and force greater in magnitude than the static friction must be applied to cause the two objects to slide on each other, and this force must be applied constantly. This force is defined as kinetic friction (Popov, 2010). The concept of static and kinetic friction applies to automobiles when they are driving on wet roads. The values of static and kinetic coefficient of friction in a dry road are 1.00 and 0.80 respectively. Similar values for a wet road are 0.60 for static and 0.40 for kinetic coefficient of friction. That implies that wet roads are more slippery than dry roads. Also, considering Newton’s second and third laws of motion, the driver must drive at a slower speed as compared to dry roads so as to be able to decelerate safely when negotiating corners as well as ensure that CAR CRASH 4 the vehicle can come to a stop at a distance which is safe for other road users. The equation which is used to calculate the braking distance is shown below (Popov, 2010). d = V2 / 2gµ where; d is the braking distance V is the initial speed of the vehicle (in meters per second) g is the acceleration caused by gravity, and its affixed value is 9.80 meters per second squared µ is the coefficient of (kinetic or static) friction between the road and the tyre. From the above equation, it can be noted that if the velocity of the vehicle is doubled; … Read more