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Done by: Liu Du Kai Ying Dexter Kuah Nicholas Lim Momentum Given by the formula: p = mass x velocity Force of Impact The force of impact on the driver when a car crash occurs is given by the formula: Momentum Time = Mass X Velocity Time As you can see, the change in momentum in this case is changed with the change in acceleration However, we are unable to change the mass of the car or the velocity at which it travels Thus, we can only extend the impact time to reduce the force via a few safety precautions in the car Seatbelt This is the most common item in all cars Protects the passenger from harm by reducing inertia Based on Newton’s 1 st law: An object will remain in a state of rest or continue traveling at constant velocity, unless acted on by another force The seatbelt can thus help to be this resistive force Seatbelt The use of the seatbelt can be explained using Newton’s 3rd law: If object A exerts a force on object B, object B will exert an equal force on object A Thus, the seatbelt in the case when the passenger is thrown forward, will exert an equal force back on the passenger, thus reducing the force acting on him Seatbelt Why the seatbelt works, is based on physics equation on impulse: In the case of a seatbelt, it extends the time of the collision, and thus reduces the average impact force Example A car is travelling at a speed of 100km/h The passengers inside are all travelling at a speed of 100km/h In the event of an accident, the car stops very fast, slowing down However, the passengers inside are still moving at 100km/h Thus, the seatbelt exerts a force back on the passenger, thus causing him to slow down and extending the time of collision, preventing more severe injuries Air bags Air bags inflate when the car decelerates extremely quickly This surrounds the passenger like a cushion Although the use of seat belts can allow the passenger’s body from flying, the passenger’s head will still experience a whiplash The body stays, but the head is thrown forward Air bags Based on Newton’s 3 rd law, the air bag will serve as the opposite force to prevent the passenger’s head from flying further in front Based on Newton’s 1 st law of inertia, an object will continue in its state of motion unless acted on by another force The airbag can thus serve as the resistive force to prevent the head from slamming into the windscreen with a great force since the time of collision is extended Car Brakes One of the most important items in a car are the ones which slow down the car’s velocity The car brakes help by increasing energy in the opposite direction, thus slowing the car’s velocity There are a few aspects of physics in a car brake 1) The brake pedal 2) The car brake itself Car Brakes The pedal uses a lever system as our legs are not strong enough to slow down the car One side of the lever in the pedal is twice as long as the other As our foot provides a small force to the longer side of the pedal the lever system allows the force to be multiplied because the force before must be equal to the force after This allows the car to slow down with enough energy Car Brakes The car brakes itself uses hydraulic pressure and friction to slow down the velocity of the car When the pedal is stepped down, the friction between the car tires and the surface of the road increases The amount of force acting in the opposite direction increases Thus, the resultant force decreases Car tires The car tires have patterns and markings on them so as to increase friction between the road surface and the car This increases friction working in the opposite direction, and thus sl0wing the car down Crumple zone The crumple zone AKA crash zone is the part of the car that will collapse upon impact Upon this collapse, the crumple zone absorbs the force of the impact, reducing the amount of force acting on the passenger Crumple zone This can be explained also with the equation of impulse During an accident, the crumple zone extends the time of the collision This thus reduces the force acting on the passengers References http://www.scienceclarified.com/everyday/Real-Life-Chemistry-Vol-3Physics-Vol-1/Momentum-Real-life-applications.html http://hyperphysics.phy-astr.gsu.edu/hbase/impulse.html http://www.physicsclassroom.com/class/momentum/u4l1c.cfm http://www.youtube.com/watch?v=i_S9qV8vLwI http://cnx.org/content/m31492/latest/ http://www.grc.nasa.gov/WWW/K-12/airplane/newton2.html http://docs.google.com/View?id=dcv8dft6_904dxf9jxvt http://www.money-zine.com/Financial-Planning/Leasing-or-Buying-aCar/Car-Safety-Features/