ase the inertia that the object has therefore increasingthe amount of force due to an increase in acceleration. Many parents often allow their children to ride in thefront seat of the car unbuckled. They say that if a collision occurs that theyll just reach over and hold thechild back. If you really look at the physics behind their theory you will see that these parents are deadwrong. What is the force required to stop a 27 kg child travelling at 25 m/s? Momentum is equal to masstimes velocity and impulse is equal to the change of momentum. Using the derived formula from theprevious statement F * t = m * Vf - Vi we see that the force exerted on the child by the seatbelt is 1687.5Newtons which is the equivalent of 172.4 kg. This force is only exerted on the body for the time it takes tobring the car to rest which is approximately 0.4 seconds. Using Newtons second law that states thatacceleration is directly proportional to the force and indirectly proportional to the mass we can see how theforce on an adult travelling at the same speed will experience a different force than that of the child. Fromthe formula derived from Newtons second law, F=m*a we see that a 67.5 kg person in the same accidentwill experience a force of 949.95 kg for 0.4 seconds by their seatbelt. This is a lot of force for one person. So I wonder how those parents with the unbuckled children in the front seat expect to hold back a childexerting 172.4 kg of force while they are trying to hold themselves from crashing into the windshield with949.5 kg of force.Newtons third law states that for every action there is an equal and opposite reaction force. Thislaw help explain why a collision at low speeds is less serious than one at high speeds. If a car exerts a smallforce on a brick wall because its speed was low then the car and its passengers will experience a force ofequal magnitude but it will be in the opposite direction. If cars of unequal mass col...
