Question

cross - disciplinary
real world applications
driving safety
read the following paragraphs, and complete the exercises below.
more than 70 percent of fatal traffic accidents are caused by improper driving. how can you
avoid becoming one of those statistics? for one thing, you can acquire an understanding of
how the laws of physics influence the movement of vehicles and the people inside of them.
inertia
part of isaac newtons first law of motion states that an object in motion tends to remain in
motion unless acted on by an outside force. furthermore, the tendency of an object to remain
in motion is related to its momentum, which is the product of the objects mass and velocity:
momentum = mass × velocity
the greater the momentum, the more difficult it is to bring a vehicle to a stop.
exercises

1. which has the greater momentum, a 1,000 - kilogram car moving with a velocity of 80

kilometers per hour or a 5,000 - kilogram truck moving with a velocity of 30 kilometers
per hour? explain your answer.

1. why should you drive a car a greater distance ahead of a truck than behind it?
2. what force opposes the motion of your car when you step on the brake pedal?

Explanation:

Step1: Calculate the momentum of the car

Use the formula \(momentum = mass\times velocity\). For the car, \(mass = 1000\space kg\) and \(velocity = 80\space km/h\). So, \(momentum_{car}=1000\times80 = 80000\space kg\cdot km/h\)

Step2: Calculate the momentum of the truck

For the truck, \(mass = 5000\space kg\) and \(velocity = 30\space km/h\). So, \(momentum_{truck}=5000\times30=150000\space kg\cdot km/h\)

Step3: Compare the two momenta

Since \(150000>80000\)

1. Truck's momentum: Using \(p = m\times v\) (\(p\) - momentum, \(m\) - mass, \(v\) - velocity), for the truck \(m = 5000\space kg\), \(v = 30\space km/h\), \(p = 5000\times30=150000\space kg\cdot km/h\). For the car \(m = 1000\space kg\), \(v = 80\space km/h\), \(p = 1000\times80 = 80000\space kg\cdot km/h\). So truck has more momentum.
2. Driving distance: A truck has greater momentum (due to larger mass). If you are ahead of a truck and it needs to stop, it takes longer (because \(F=\frac{\Delta p}{\Delta t}\), larger \(p\) means more force or more time to stop). If you are behind, you can react to its braking more easily as you can see its brake lights. But if you are ahead, the truck's inability to stop quickly (because of high momentum) can lead to a collision if you brake suddenly.
3. Force when braking: Friction (between the brake pads and the wheels, and between the wheels and the road) opposes the motion of the car.

Answer:

The truck has a greater momentum.