### Witnessed a hit-and-run accident

Assignment Help Physics
##### Reference no: EM13543506

You witnessed a hit-and-run accident when you were driving a car at velocity u towards a radio station very far ahead on the street. Here is how it happened: you were listening to the radio when you \saw" a car driving towards you hit a person standing by the bus stop, everything happened in front of you and was closer than the radio station. The accident happened when your favorite song from the radio just started, and after the accident the car didn't change its velocity at all. You decided to stop the car by crashing into him (without changing your velocity); and when your heroic crash stopped the car, your favorite song from the radio just ended. Now the police wants you to help them figure out the details of the accident.

As a warm up, let's do some multiple choice/True-or-False problems first : According to another witness, code name witness A, who stood by the bus stop, the victim struggled for a while before he died. Witness A doesn't have a watch, but he was also listening to that radio and he reported that when the poor man died, it's just at the end of that song you were listening.

1. In the rest frame, the victim died
a) before the car was stopped by you.
b) at the time the car was stopped by you.
c) after the car was stopped by you.

2. It's possible that in some frame the victim died after the car was stopped by you.

3. According to witness A, after being hit the victim called his girlfriend but could not nish his last words before he died. Due to time dilation, there exists some other frame, where the poor man had more time before he died, and hence in such a frame, the man nished his last words before he died.

4. Because of the velocity addition formula, the speed reading by the man causing the accident diers from the reading of his speed on the ground.

5. While from the point of view of witness A, the accident took place right at the bus stop, due to Lorentz contraction the accident appeared to happen at a closer place to you and hence it didn't happen at bus stop from your perspective.

6. The man claimed that due to Lorentz contraction although it looked like he would hit the victim, there should actually be enough margin (in the direction perpen-dicular to the direction he was moving) for him to pass the victim safely. Thus in principle, he shouldn't be responsible for the accident.

7. (8 pts) Now, the police wants to know if the car was speeding. They are able to get the measurement between the bus-stop and the wreckage of your car, and the distance is L. But they don't have a record of the time t it took for the car to travel that distance and calculate the speed. To help them, you realize that the length of your favorite song from the radio station might help since you know the length of the song is T when you usually listen to it from your CD player. Find the speed v of the car. (Hint, don't forget that when you \saw" the accident it's actually already after the accident happened since it took time for the light to travel from where it happened to your eye).

### Previous Q& A

#### What is the power drawn from the electric outlet

An AC adapter for a telephone answering machine uses a transformer to reduce the line voltage of 120 V to a voltage of 5.00 V. The RMS current delivered to the answering machine is 400 mA. If the primary (input) coil of the transformer has 600 tur..

A resonant circuit in a radio receiver is tuned to a certain station when the inductor has a value of 0.311 mH and the capacitor has a value of 16.4 pF. Calculate the frequency of the radio station.?

#### What is the frequency of the source

An AC voltage source has an output of ?V = 163.0 sin(582t) Volts. Calculate the RMS voltage. What is the frequency of the source?

#### A dump truck designed to carry grain is shown

A dump truck designed to carry grain is shown. The dump bed is actuated by a hydraulic cylinder AB. If the combined weight of the dump bed plus its load is 800 lb, and the bed is at the position shown, determine the forces acting on the bed at B and ..

#### Calculate the magnetic moment of the loop

A current of 14.0 mA is maintained in a single circular loop of 3.80 m circumference. A magnetic field of 0.610 T is directed parallel to the plane of the loop. (a) Calculate the magnetic moment of the loop. Please have answer in mA · m2

#### The rectangle and the circuit containing the long wire

Consider again the long wire near a small wire rectangle. The long wire is part of a circuit. The circuit is small enough that all the approximations we've used in class are good, but the wire near the rectangle is much longer than the rectangle. ..

#### How long will it take to assume the original course again

Ship moving initially at 10.7 m/s due North, drifts due NE at the same speed. To correct the bearing, the captain accelerates the engine and turns the rudder NW. If the engines deliver a constant acceleration of 4.4 m/s2, how long will it take to a..

#### Determine the water velocity at inlet and outlet

A 90° elbow is used to direct water (? = 1000 kg/m3) flow at a rate of 25 kg/s in a horizontal pipe upward. The di-ameter of the entire elbow is 10 cm. The elbow discharges water into the atmosphere, and thus the pressure at the exit is the local ..

#### Acceleration of the plate when the jet first strikes

A horizontal 5-cm diameter water jet with a velocity of 18 m/s impinges normally upon a vertical plate of mass 1000 kg. The plate rides on a nearly frictionless track and is initially stationary. When the jet strikes the place, the plate begins to..

#### A very large plane of charge is oriented horizontally

A very large plane of charge is oriented horizontally and has a constant charge distribution over the plane. A small insulating ball has charge +8.78 nC and mass 0.076 g. If the levitates 2.62 cm beneath the plane, and remains stationary, what is the..

### Similar Q& A

#### Q1 a 60kg ball of clay is thrown horizontally at 40 ms

q1. a 60kg ball of clay is thrown horizontally at 40 ms toward a 1.6kg block sitting at rest on a frictionless hi

#### How much time is required for projectile to come up to speed

Scientists are experimenting with a kind of gun that may eventually be used to fire payloads directly into orbit. How much time is required for the projectile to come up to speed

#### Find out the acceleration of the sled and child

the snow exerts a retarding force on the sled that points opposite to the direction of motion, and has a magnitude of 57. Find out the acceleration of the sled and child.

#### Estimate its speed when it reaches the bottom

A roller coaster reaches the top of the steepest hill with a speed of 6.0 km/h. Estimate its speed when it reaches the bottom

#### What speed does the arrow leave the bow

An archer puts a 0.33 kg arrow to the bowstring. An average force of 183 N is exerted to draw the string back 1.3 m. suppose that air resistance is negligible.

#### How many nuclei are in the beam

A beam of nuclei is used for cancer therapy. Each nucleus has an energy of 108 MeV, How many nuclei are in the beam

#### Find the diameter of the path followed by the alpha particle

An alpha particle, which is a helium nucleus, has a mass of 6.64*10^-27 kg. It is travleing horizontally at 42.3 km/s when it enters a uniform, What is the diameter of the path followed by the alpha particle

#### Find by how much will it miss the target

A hunter aims directly at a target (on the same level) 150 m away. If the bullet leaves the gun at a speed of 220 m/s, by how much will it miss the target

#### What rate must the magnetic field change with the time

A uniform magnetic field is normal to the plane of a circular loop 10 cm in diameter made of copper wire (diameter 2.5 mm). At what rate must the magnetic field change with the time if an induced current of 10 A is to appear in the loop? The resistiv..

#### How far will it travel before becoming airborne

How far will it travel before becoming airborne

#### What is the trucks speed

Two loudspeakers emit 500Hz notes. One speaker sits on the ground. The other speaker is in the back of a pickup truck, What is the truck's speed

#### Calculate the focal length and optical power of the lens

A relaxed crystalline lens has a refractive index n=1.42 and radii of curvature R1=+10.0mm, Calculate the focal length and optical power of the lens