9. You are part of a citizen's group evaluating the safety of a high school athletic program. To help

judge the diving program you would like to know how fast a diver hits the water in the most

complicated dive. The coach has his best diver perform for your group. The diver, after jumping

dive, she passes near a lower diving board which is 3.0 m above the water. With your trusty stop

watch, you determine that it took 0.20 seconds to enter the water from the time the diver passed

the lower board. How fast was she going when she hit the water?

10. As you are driving to school one day, you pass a construction site for a new building and stop to

watch for a few minutes. A crane is lifting a batch of bricks on a pallet to an upper floor of the

building. Suddenly a brick falls off the rising pallet. You clock the time it takes for the brick to hit

the ground at 2.5 seconds. The crane, fortunately, has height markings and you see the brick fell

off the pallet at a height of 22 meters above the ground. A falling brick can be dangerous, and

you wonder how fast the brick was going when it hit the ground. Since you are taking physics,

you quickly calculate the answer.

11. Because of your knowledge of physics, and because your best friend is the third cousin of the

director, you have been hired as the assistant technical advisor for the associate stunt coordinator

on a new action movie being shot on location in Minnesota. In this exciting scene, the hero

pursues the villain up to the top of a bungee jumping apparatus. The villain appears trapped but to

create a diversion she drops a bottle filled with a deadly nerve gas on the crowd below. The

script calls for the hero to quickly strap the bungee cord to his leg and dive straight down to grab

the bottle while it is still in the air. Your job is to determine the length of the unstretched bungee

cord needed to make the stunt work. The hero is supposed to grab the bottle before the bungee

cord begins to stretch so that the stretching of the bungee cord will stop him gently. You estimate

that the hero can jump off the bungee tower with a maximum velocity of 10 ft/sec. straight down

by pushing off with his feet and can react to the villain's dropping the bottle by strapping on the

bungee cord and jumping in 2 seconds.

12. You are helping a friend devise some challenging tricks for the upcoming Twin Cities Freestyle

Skateboard Competition. To plan a series of moves, he needs to know the rate that the

skateboard, with him on board, slows down as it coasts up the competition ramp which is at 30°

Linear Kinematics

to the horizontal. Assuming that this rate is constant, you decide to have him conduct an

experiment. When he is traveling as fast as possible on his competition skateboard, he stops

pushing and coasts up the competition ramp. You measure that he typically goes about 95 feet in

6 seconds. Your friend weighs 170 lbs. wearing all of his safety gear and the skateboard weighs

6 lbs.

13. You have a summer job working for a University research group investigating the causes of the

ozone depletion in the atmosphere. The plan is to collect data on the chemical composition of the

atmosphere as a function of the distance from the ground using a mass spectrometer located in the

nose cone of a rocket fired vertically. To make sure the delicate instruments survive the launch,

your task is to determine the acceleration of the rocket before it uses up its fuel. The rocket is

launched straight up with a constant acceleration until the fuel is gone 30 seconds later. To collect

enough data, the total flight time must be 5.0 minutes before the rocket crashes into the ground.

14. You have landed a summer job as the technical assistant to the director of an adventure movie

shot here in Minnesota. The script calls for a large package to be dropped onto the bed of a fast

moving pick-up truck from a helicopter that is hovering above the road, out of view of the

camera. The helicopter is 235 feet above the road, and the bed of the truck is 3 feet above the

road. The truck is traveling down the road at 40 miles/hour. You must determine when to cue

the assistant in the helicopter to drop the package so it lands in the truck. The director is paying

$20,000 per hour for the chopper, so he wants you to do this successfully in one take.

15. Just for the fun of it, you and a friend decide to enter the famous Tour de Minnesota bicycle race

from Rochester to Duluth and then to St. Paul. You are riding along at a comfortable speed of 20

mph when you see in your mirror that your friend is going to pass you at what you estimate to be a

constant 30 mph. You will, of course, take up the challenge and accelerate just as she passes you

until you pass her. If you accelerate at a constant 0.25 miles per hour each second until you pass

her, how long will she be ahead of you?

16. In your new job, you are the technical advisor for the writers of a gangster movie about Bonnie

and Clyde. In one scene Bonnie and Clyde try to flee from one state to another. (If they got

across the state line, they could evade capture, at least for a while until they became Federal

fugitives.) In the script, Bonnie is driving down the highway at 108 km/hour, and passes a

concealed police car that is 1 kilometer from the state line. The instant Bonnie and Clyde pass the

writers want to know if they make it across the state line before the pursuing cop catches up with

them.

17. The University Skydiving Club has asked you to plan a stunt for an air show. In this stunt, two

skydivers will step out of opposite sides of a stationary hot air balloon 5,000 feet above the

ground. The second skydiver will leave the balloon 20 seconds after the first skydiver but you

want them both to land on the ground at the same time. The show is planned for a day with no

Linear Kinematics

wind so assume that all motion is vertical. To get a rough idea of the situation, assume that a

as the parachute is opened, the skydiver falls with a constant velocity of 10 ft/sec. If the first

skydiver waits 3 seconds after stepping out of the balloon before opening her parachute, how long

must the second skydiver wait after leaving the balloon before opening his parachute?

18. Because parents are concerned that children are learning "wrong" science from TV, you have

been asked to be a technical advisor for a science fiction cartoon show on Saturday morning. In

the plot, a vicious criminal (Natasha Nogood) escapes from a space station prison. The prison is

located between galaxies far away from any stars. Natasha steals a small space ship and blasts

off to meet her partners somewhere in deep space. The stolen ship accelerates in a straight line at

the ship coasts at a constant velocity. Meanwhile, the hero (Captain Starr) learns of the escape

while dining in the prison with the warden's daughter (Virginia Lovely). Of course he immediately

(as soon as he finishes dessert) rushes off the recapture Natasha. He gives chase in an identical

ship, which has an identical maximum acceleration, going in an identical direction. Unfortunately,

Natasha has a 30 minute head start. Luckily, Natasha's ship did not start with a full load of fuel.

With his full load of fuel, Captain Starr can maintain maximum acceleration for 15 minutes. How

long will it take Captain Starr's ship to catch up to Natasha's?

19. Because parents are concerned that children are learning "wrong" science from TV, you have

been asked to be a technical advisor for a new science fiction show. The show takes place on a

space station at rest in deep space far away from any stars. In the plot, a vicious criminal (Alicia

Badax) escapes from the space station prison. Alicia steals a small space ship and blasts off to

meet her partners somewhere in deep space. If she is to just barely escape, how long do her

partners have to transport her off her ship before she is destroyed by a photon torpedo from the

space station? In the story, the stolen ship accelerates in a straight line at its maximum possible

coasts at a constant velocity. Meanwhile, the hero of this episode (Major Starr) learns of the

escape while dining with the station's commander. Of course she immediately rushes off to fire

photon torpedoes at Alicia. Once fired, a photon torpedo travels at a constant velocity of 20,000

m/s. By that time Alicia has a 30 minute (1800 seconds) head start on the photon torpedo.

20. You want to visit your friend in Seattle over Winter-quarter break. To save money, you decide to

travel there by train. But you are late finishing your physics final, so you are late in arriving at the

train station. You run as fast as you can, but just as you reach one end of the platform your train

departs, 30 meters ahead of you down the platform. You can run at a maximum speed of 8 m/s

and the train is accelerating at 1 m/s. You can run along the platform for 50 meters before you

reach a barrier. Will you catch your train?

21. Because of your knowledge of physics, you have been assigned to investigate a train wreck

between a fast moving passenger train and a slower moving freight train both going in the same

direction. You have statements from the engineer of each train and the stationmaster as well as

some measurements which you make. To check the consistency of each person's description of

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the events leading up to the collision, you decide to calculate the distance from the station that the

collision should have occurred if everyone were telling what really happened and compare that

with the actual position of the wreck which is 0.5 miles from the station. In this calculation you

decide that you can ignore all reaction times. Here is what you know:

• The stationmaster claims that she noted that the freight train was behind schedule. As

regulations require, she switched on a warning light just as the last car of the freight train

passed her.

• The freight train engineer says he was going at a constant speed of 10 miles per hour.

• The passenger train engineer says she was going at the speed limit of 40 miles per hour when

she approached the warning light. Just as she reached the warning light she saw it go on and

immediately hit the brakes.

• The warning light is located so that a train gets to it 2.0 miles before it gets to the station.

• The passenger train slows down at a constant rate of 1.0 mile per hour for each minute as

soon as you hit the brakes.

DO ONLY THE PROBLEM SOLVING STEPS NECESSARY TO FOCUS THE PROBLEM

PROBLEM.