Physics

Topics: Automobile safety, Seat belt, Classical mechanics Pages: 7 (2703 words) Published: September 16, 2014
Change of momentum is related to the forces acting on the vehicle or the driver. Explain how we can increase the safety of the driver based on the above statement.

Momentum of an object can be defined as the product of the mass of the object and its velocity. The unit of momentum is kgms-1. Momentum is a vector quantity, and it has both magnitude and direction. Its direction is the same as the direction of the object’s velocity. Momentum = mass x velocity

p = m v
Momentum can also be defined as inertia in motion. To have momentum, the object must be moving. Momentum tells how hard it is to get something to stop or to change directions. Every moving object has momentum and any object with momentum is going to be hard to stop. To stop such an object, it is necessary to apply a force against its motion for a given period of time. The more momentum the object has, the harder it is to be stopped. Thus, it would require a greater amount of force or a longer amount of time or both to bring such an object to a halt. Force acting for a given amount of time will change an object's momentum. As the force acts upon the object for a given amount of time, the object's velocity is changed, and hence, the object's momentum is changed.1 If the force acts opposite the object's motion, it slows the object down. If the force acts in the same direction as the object's motion, then the force speeds the object up. Either way, a force will change the velocity of an object. And if the velocity of the object is changed, then the momentum of the object is changed. Relating momentum to Newton’s Law of Motion, Newton’s First Law of Motion, which states that an object will remain at rest or keep moving at constant velocity unless it is acted by an external force, keeps the idea that the momentum of an object remains the same unless the object experience an external force, because an object travelling at constant velocity will have constant momentum. Meanwhile, Newton’s Second Law of Motion links the idea of the net force acting on an object and its momentum. It implies that the net force acting on an object is directly proportional to the rate of change of the linear momentum of that object. The net force and the change in momentum are in the same direction. It can also be said that the net force is equal to the rate of change in momentum.2

In a collision, an object experiences a force for a given amount of time that results in its mass undergoing a change in velocity. The product of the force and time is called an impulse.
If an object puts an impulse on another object, the momentum of both objects will change. Therefore, it can be concluded that impulse is equal to change in momentum and the equation can be written as

Automobiles consist of several objects, including the vehicle itself, the passengers inside and any other loose objects in the vehicle. Unless the objects inside the car are restrained, they will continue moving at whatever speed the car is travelling, even if the car is stopped by a crash. So when a car stops suddenly due to a collision with another object such as another car, a tree, pole, guardrail, etc. the car undergoes deceleration in which the car's acceleration decreases very quickly in a short period of time. As the car collides with another object, the other object provides the force, which changes the speed and direction. The car stops going in the direction it was going in, and in some cases bounces back depending how hard of a force hits it or how much momentum the car had. The passenger inside the car however, will continue moving in their same direction and speed, which is the same as the direction and speed in which the car was going, until they are met by an equal and opposite force. As a result, they will keep on moving and been thrown out of the seat due to inertia effect. As according to Newton’s Second Law, in the case of vehicle accident such as car crash, since the momentum changes instantly, the...
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