# Seat belts and air bags save lives by reducing the forces exerted on the driver and passengers in an automobile collision. Cars are designed with a "crumple zone" in the front of the car. In the event of an impact, the passenger compartment decelerates over a distance of about 1 m as the front of the car crumples. An occupant restrained by seat belts and air bags decelerates with the car. By contrast, an unrestrained occupant keeps moving forward with no loss of speed (Newton's first law!) until hitting the dashboard or windshield. These are unyielding surfaces, and the unfortunate occupant then decelerates over a distance of only about 5 mm . Part APart complete A 60 kg person is in a head-on collision. The car's speed at impact is 15 m/s . Estimate the net force on the person if he or she is wearing a seat belt and if the air bag deploys.

The net force is 1350 kN

Solution:

As per the question:

Mass of man, m = 60 kg

Initial speed of the car, v = 15 m/s

Final speed of the car, v' = 0 m/s

Distance covered by the person before coming to rest, d = 5 mm =

By using the third eqn of motion:

Thus the force on the person can be given by:

F = ma =

## Related Questions

Try rubbing a plastic pen through your hair, and you'll find that you can pick up a tiny scrap of paper when the pen is about one centimeter above the paper. from this simple experiment you can estimate how much an atom in the paper is polarized by the pen! you will need to make several assumptions and approximations.

When you rub the plastic pen through your hair, you create static electricity because you increase the energy of the electrons due to collision brought about by the rubbing motion. It will then create a magnetic field on the plastic pen. That's why you can pick up the paper using the pen. The concept used here is electromagnetism.

An accelerometer is a device that uses the extension of a spring to measure acceleration in terms of Earth's gravitational acceleration (g). What is the approximate acceleration if this accelerometer spring is extended just 0.43 centimeters?. . a) 0.24 g. b) 0.80 g. c) 2.00 g. d) 2.40 g

In your question explains that an accelerometer is a device that uses the extension spring to measure acceleration in terms of Earth's Gravitational accelerations. So if this device is extended just 0.43 centimeters the possible accelerations is letter B. 0.80 g

0.80

Explanation:

The first person to answer was correct

It takes 180 kj of work to accelerate a car from 21.0 m/s to 27.0 m/s. what is the car's mass?

558888544446556313321

F Penny's piston is wider than Pauly's, who is pushing with greater force?

It would depend on who is stronger but it is likely that Penny would be creating larger pressure because the surface area is less. If this is part of a question where the pressure for both is the same then Pauly is pushing with greater force, I know this because force/area=pressure and when the surface area is larger the force must be greater as well.

Hope this helps :)
A Penny is exerting the greater force.
B Pauly is exerting the greater force.
C They are both using equal force.
Think its A or C

How does a radio station know how many listeners?

I belive this is due to radio ratings.
hope this helps!
Hello there,
There is a ratings service that most radio stations in the top 200 cities subscribe to. So through the rating services the radio station will know

Hope this helps :))

~Top

A. Your friend strikes a gong across the room from you. How does the gong make a sound? How does the energy of the sound reach you? Why don't you feel a push of air when you hear the sound? Write three or four sentences to state your answers. b. Describe the amplitude and frequency of the sound wave for a low, soft note. Identify the characteristic of the sound that is connected to each wave property.

c. Write two or three sentences to define intensity and to state how intensity changes as the distance from the sound is decreased.

d. A sound is transmitted through equal lengths of aluminum and alcohol. In which material does sound travel faster? Write one or two sentences to explain your reasoning.

e. An ambulance with its siren wailing is moving away from an observer. Write two or three sentences to compare the pitch of the sound for the observer with the pitch for the ambulance driver. What is the term used to describe this phenomenon?

Explanation:

(a) Sound waves consists of rarefaction and compression. Sound needs a medium to travel. When a sound travels through a medium, the particles of the air vibrate. There will be compression where the density of air particle is more and rarefaction where there will be less density of air particles.

Sound is a form of energy. It transfers the energy from particle of air to another particle. In this way, a person able to hear the sound.

(b)

The loudness of the sound depends on the amplitude. Higher the amplitude, more will be loudness. Lower the amplitude, lesser will be loudness. The frequency of the sound depends on the pitch. The higher frequency correspondence to high pitch. The lower frequency correspondence to low pitch.

(c)

The intensity of the sound obeys the inverse square law. The intensity of the sound is inversely proportional to square of the distance. As the distance increases the intensity of the sound decreases.

(d)

Sound travels faster in the solid than liquid and gas. A sound travels faster in aluminium than alcohol.

(e)

An ambulance with its siren wailing is moving away from an observer. The difference in the sound of the siren is due to the phenomenon called Doppler effect. This phenomenon is observed when the source is moving with respect to an observer.

When an ambulance approaches then the siren sounds louder and more shrill. But there is a sudden change in the pitch when an ambulance overtakes an observer. There is an apparent increase in the frequency of the wave.

a) The gong elastically deflects and then pushes the molecules of air making sound. Then these molecules push other molecules along the direction of the sound. The energy is small and we can't feel it. However try stand in front of loud low frequency speaker, you will feel it without your ears.

b) Low soft noise: low frequency, low amplitude. frequency is responsible for making bass or high sounds, amplitude makes sound loud or silent.

c) Sound intensity is power per area. Increase distance - area of a spherical sound wave front will increase and intensity will decrease.

d) Speed of sound depends on stiffness and density of a medium,. Without any calculations I'd say that the speed of sound in alcohol is higher.

e) The Doppler effect. For ambulance driver the sound will be higher and louder than for observer cause wavelength will increase, frequency decrease outside the car.

What is true about the relationship between the kinetic energy of molecules in an object and the objects temperature? A. As the kinetic energy of molecules decreases the temperature increases
B. As the temperature increases the kinetic energy of the molecules decreases
C. The total kinetic energy of the molecules is not affected by a change in temperature
D. The kinetic energy always increases whether the temperature increases or decreases

As the temperature increases the kinetic energy of the molecules increases, if u add more heat you get more kinetic energy.

A neutral K meson at rest decays into two π mesons, which travel in opposite directions along the x axis with speeds of 0.828c. If instead the K meson were moving in the positive x direction with a velocity of 0.486c, what would be the velocities of the two π mesons?

The velocity of the two -meson are 0.574 in positive direction and - 0.9367c in the negative direction along X-axis

Solution:

As per the question:

The speed of the -meson along x-axis, v' = 0.828c

The speed of the K-meson along positive x-axis, v'' = 0.486c

Now, to calculate the velocities of the two -meson:

Velocity of the first -meson, :

Velocity of the second -meson, :

and

Explanation:

To solve this problem, we need to use the following formula

Givens:

In same direction, we have

Notice, that we just replaced each given value, and solve basic operations.

In different direction,

As you can observe, to solve this kind of problem, you just neet to consider the right sign of each velocity, when they are in the same direction, they must have the same sign, but when they are in opposite direction, they must have different signs.

You sit at the outer rim of a Ferris Wheel that rotates 2 revolutions per minute (RPM). What would your rotational speed be if you were instead clinging to a position halfway from the center to the outer rim. Be sure to provide at least 3 to 4 complete content related sentences and show any work needed to support your answer