The probability that a call to an emergency help line is answered in less than 15 seconds is 0.85. Assume that all calls are independent. (a) What is the probability that exactly 7 of 10 calls are answered within 15 seconds? (b) What is the probability that at least 16 of 20 calls are answered in less than 15 seconds? (c) For 50 calls, what is the mean number of calls that are answered in less than 15 seconds? (d) Repeat parts (a)–(c) using the normal approximation.

Hos pitals typically req uire backup generators to provide electricity in the event of a power outage. Assume that emergency backup generato rs fai l 22% of the times when they are needed (based on data from Arshad Mansoor, senior vice president with the Electric Power Research In stitute). A hospital has two backup generators so that power is avail able if one of them fails during a power outage. Find the probability of having a working generator in the event of a power outage. Is that probability high enough for the hospital?

A driver makes an emergency stop and inadvertently locks up the brakes of the car, which skids to a stop on dry concrete. Consider the effect of heavy rain on this scenario. Using the values in Table 1, determine how much farther the car would skid (expressed as a percentage of the dry-weather skid) if the concrete were wet instead. What does this question imply about driving safely?

Table 1 Coeffi cients of Kinetic Friction for Rubber on Concrete

Surface	$\mu_{\mathrm{K}}$
rubber on dry concrete	$0.85$
rubber on wet concrete	$0.45$

You are working in the emergency department (ED) of a community hospital when the ambulance arrives with A.N., an $18$-year-old woman who was caught in a house fire. She was sleeping when the fire started and managed to make her way out of the house through thick smoke. The emergency medical system crew initiated humidified oxygen at $15 \mathrm{~L} / \mathrm{min}$ per nonrebreather mask and started a $16$-gauge IV with lactated Ringer's solution. On arrival to the ED, her vital signs are $100/66, 125, 34$, $\mathrm{SaO}_2 93 \%$. An additional $16$-gauge IV is inserted. She appears anxious and in pain.

$$\begin{aligned} &\text { Laboratory Test Values }\\ &\begin{array}{ll} \text { Hgb } & 20 \mathrm{~g} / \mathrm{dL} \\ \text { Hct } & 51 \% \\ \mathrm{~K} & 4.9 \mathrm{mEq} / \mathrm{dL} \\ \mathrm{Na} & 133 \mathrm{mEq} / \mathrm{dL} \\ \mathrm{Cl} & 100 \mathrm{mEq} / \mathrm{dL} \\ \text { Glu } & 159 \mathrm{mg} / \mathrm{dL} \\ \text { BUN } & 28 \mathrm{mg} / \mathrm{dL} \\ \text { Cre } & 1.0 \mathrm{mg} / \mathrm{dL} \end{array} \end{aligned}$$

Interpret A.N.'s laboratory results.

Study of why EMS workers leave the job. A study of fulltime emergency medical service (EMS) workers published in the Journal of Allied Health (Fall 2011) found that only about 3% leave their job in order to retire. (See Exercise $3.45$, p. 158.) Assume that the true proportion of all fulltime EMS workers who leave their job in order to retire is $p=.03$. In a random sample of 1,000 full-time EMS workers, let $\hat{p}$ represent the proportion who leave their job in order to retire. Compute $P(\hat{p}<.05)$. Interpret this result.

An accident victim who had not been wearing a seat belt received trauma to his forehead when he was thrown against the windshield. The physicians in the emergency room worried that his brain stem may have been driven inferiorly through the foramen magnum. To help assess this, they quickly took a standard X-ray film of his head and searched for the position of the pineal gland. How could anyone expect to find this tiny, boneless gland in a radiograph?

Two small liquid-propellant rocket motors are mounted at the tips of a helicopter rotor to augment power under emergency conditions. The diameter of the helicopter rotor is $7 \mathrm{~m}$, and it rotates at $1 \mathrm{rev} / \mathrm{s}$. The air enters at the tip speed of the rotor, and exhaust gases exit at $500 \mathrm{~m} / \mathrm{s}$ with respect to the rocket motor. The intake area of each motor is $20 \mathrm{~cm}^2$, and the air density is $1.2 \mathrm{~kg} / \mathrm{m}^3$. Estimate the power provided by the rocket motors. Ignore the mass rate of flow of fuel in this calculation.

For many years Colonel John P. Stapp, USAF, held the world’s land speed record. He participated in studying whether a jet pilot could survive emergency ejection. On March $19$, $1954$, he rode a rocket-propelled sled that moved down a track at $632$ mi/h. He and the sled were safely brought to rest in $1.40$ s. Determine (a) the negative acceleration he experienced and (b) the distance he traveled during this negative acceleration, assumed to be constant.

Just an instant before reaching the very bottom of a semicircular section of a roller coaster ride, the automatic emergency brake inadvertently goes on. Assume the car has a total mass of 750 kg, the radius of that section of the track is 55.0 m, and the car entered the bottom after descending vertically (from rest) 25.0 m on a frictionless straight incline. If the braking force is a steady 1700 N, determine (a) the car's centripetal acceleration (including direction), (b) the normal force of the track on the car, (c) the tangential acceleration of the car (including direction), and (d) the total acceleration of the car.

Suppose an emergency van has a single-tone siren with the pitch of the musical note $\mathrm{G}$. If the van is traveling at $80 \mathrm{mph}$ approaching a standing observer, name the pitch the observer hears (rounded to the nearest tenth) and the musical note closest to that pitch.

Pitch of an Octave of Musical Notes in Hertz $(\mathrm{Hz})$

$$\begin{aligned} &\begin{array}{c|c} \hline Note & Pitch \\ \hline Middle\ C & 261.63 \\ \hline D & 293.66 \\ \hline E & 329.63 \\ \hline F & 349.23 \\ \hline G & 392.00 \\ \hline A & 440.00 \\ \hline B & 493.88 \\ \hline \end{array} \end{aligned}$$

An emergency drain pump, shown in figure, should be able to pump $0.1 \mathrm{~m}^3 / \mathrm{s}$ of liquid water at $15^{\circ} \mathrm{C}, 10 \mathrm{~m}$ vertically up, delivering it with a velocity of $20 \mathrm{~m} / \mathrm{s}$. It is estimated that the pump, pipe, and nozzle have a combined isentropic efficiency expressed for the pump as $60 \%$. How much power is needed to drive the pump?

In each of the following sentences, circle any letter that should be capitalized and draw a slash (\/) through any letter that should be lowercase. **Example 1**. $\text{\textcircled}{\text{{d}}}$id you ask $\text{\textcircled}{\text{{d}}}$r. fishbein or her ${\sout{\text{D}}}$ental ${\sout{\text{A}}}$ssistant about your toothache during your appointment last $\text{\textcircled}{\text{{f}}}$riday? “In case of an Emergency,” the notice read, “Please call $911$ to reach ems or the police.”

Study of why EMS workers leave the job. A study of fulltime emergency medical service (EMS) workers published in the Journal of Allied Health (Fall 2011) found that only about 3% leave their job in order to retire. (See Exercise $3.45$, p. 158.) Assume that the true proportion of all fulltime EMS workers who leave their job in order to retire is $p=.03$. In a random sample of 1,000 full-time EMS workers, let $\hat{p}$ represent the proportion who leave their job in order to retire. Compute $P(\hat{p}>.025)$. Interpret this result.

(a) A light-rail commuter train accelerates at a rate of 1.35 m/s². How long does it take to reach its top speed of 80.0 km/h, starting from rest? (b) The same train ordinarily decelerates at a rate of 1.65 m/s². How long does it take to come to a stop from its top speed? (c) In emergencies, the train can decelerate more rapidly, coming to rest from 80.0 km/h in 8.30 s. What is its emergency acceleration in meters per second squared?