Name (printed) _______________________________
First Day Stamp
QUESTIONS AND PROBLEMS
LINEAR MOTION
1.
A physics student leaves home, walks to school (4 blocks east) and then returns home for lunch. After
lunch, she returns to school.
a. What is the distance of her journey?
b. What is the displacement of her journey?
2.
A skydiver, with parachute unopened, falls 625 m in 15.0 s. Then he opens his parachute and falls another
356 m in 142 s. What is his average speed for the entire fall?
3.
A car drives according to the diagram to the right. Assume that there is
a 1.0-hour rest period after the first leg of the trip.
a. Determine the average speed for the trip.
60 mph for 0.25 h
60 mph for 0.25 h
30 mph for 0.50 h
b. Determine the average velocity for the trip.
4.
40 mph for 0.50 h
You maintain a speed of 115 mph for 2.0 hours. After resting for 45 minutes, you then return along the
same route to where you started. On the way back, you hold it down to 55 mph. What is your average speed
for the entire trip?
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5.
The F-15 is one of the U.S. Air Force’s fastest jets, capable of a maximum
speed of Mach 2.5 (two-and-a-half times the speed of sound). If an F-15 at
Travis AFB were required to scramble to a problem in Sacramento
(50 miles away), what is the fewest number of minutes it would take to get
there?
6.
One of the methods that the Washington D.C. Police Department uses to catch speeders is to trigger
multiple photographs of cars that pass through an automated radar zone at excessive speed. The
photographs below were taken 0.20 s apart. The marker lines are five feet apart. The speed limit in this
zone was 45 mph. By how much was this car exceeding the speed limit?
7.
A physics teacher who lives 30 miles from school is frustrated by the low speed limit of 65 mph. He
decides to go 80 mph instead. How many minutes of time does he save driving at the higher speed?
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8.
High school cross-country courses are 5 km long. Let’s say the fastest person on the team can complete the
course with an average speed of 5.21 m/s and the slowest can complete the course with an average speed of
4.27 m/s. If the fastest runner wants to run the course so that he crosses the finish line at the same time as
the slowest runner, how much time must he wait to start running after the slowest runner begins?
9.
The Boeing 747 can take up to 75 seconds to
reach its takeoff speed of approximately 90 m/s.
What is its average acceleration during takeoff?
10. When the FA-18 Hornet takes off from an aircraft carrier, it is accelerated at about 75 m/s2 for two seconds.
At what speed (in MPH) does it leave the deck?
11. A car drives for 1.5 hours at 60 mph east. Then the driver rests for an hour. Finally, the car drives for 3.0
hours at 40 mph south. Determine the average speed for the trip.
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12. Determine the average velocity for the trip in the problem #11.
13. A speed trap is set up over a distance of 1,000 m. You are moving at a speed of 35 m/s for 425 m before
you become aware of the police department airplane overhead tracking your motion. What is the maximum
speed you can travel over the remainder of the 1,000 m in order for your average speed to be under the
posted speed limit of 25 m/s?
14. Two bullies want to get you. The three of you are on a narrow path that you can’t get off. And … you’re in
the middle. They’re separated by one mile when they start running toward you. They each run at six mph,
but you can run at 10 mph. If you initially start out right in front of one of them and run back and forth the
full distance between bullies, how much distance will you have covered by the time they finally catch you?
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For each of the following questions, give clear and complete evidence for your choice in the space provided.
1. _____
2. _____
3. _____
4. _____
An average speed of zero means:
a. no motion
b. possible motion
c. definite motion
An average velocity of zero means:
a. no motion
b. possible motion
c. definite motion
A distance of zero means:
a. no movement
b. possible movement
c. definite movement
A displacement of zero means:
a. no movement
b. possible movement
c. definite movement
5. _____
It is possible to have a changing velocity even if the speed is constant.
a. true
b. false
6. _____
It is possible to have a changing speed even if the velocity is constant.
a. true
b. false
7. _____
An object travels 8 meters in the first second of travel, 8 meters again during the next second of travel,
and 8 meters again during the third second. Its acceleration is
a. 0 m/s2
b. 5 m/s2
c. 8 m/s2
d. 10 m/s2
e. more than 10 m/s2
8. _____
The following are series of speeds at the end of a 1 sec, 2 sec, 3 sec, and 4 sec interval. Which series
shows uniform acceleration?
a. 2 m/s, 3 m/s, 5 m/s, 8 m/s
c. 2 m/s, 4 m/s, 6 m/s, 8 m/s
b. 2 m/s, 4 m/s, 16 m/s, 256 m/s
d. 2 m/s, 8 m/s, 18 m/s, 32 m/s
9. _____
A car, starting at 10 m/s, accelerates at a rate of 6 m/s2 for 5 s. It maintains its speed for 10 s and then
slows at a rate of -2 m/s2 for 8 s. What is its final speed?
a. -6 m/s
b. 15 m/s
c. 24 m/s
d. 30 m/s
e. 56 m/s
Move ahead
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100% CORRECT
LABETTE
PHYSICS OF A PLASTIC TOY POPPER
INTRODUCTION
Once you understand a bit about the physics of
motion, you look at toys much differently. You begin
to look at toys critically, in terms of how many
principles of physics they illustrate. A toy store
becomes even more provocative and exciting than
when you were a kid. The balloon that you blow up
and release before tying off the end is obeying
Newton’s Third Law of Motion. The spinning top
that seems to defy gravity is an example of a rotating
body obeying the Law of Conservation of Angular
Momentum.
There used to be a toy store in Petaluma called
Aunt Julie’s. It was owned by a man named Ken (that
always seemed odd to me). Ken loved kids and he
had a great toy store. A kid could walk into his store
and, with just about any amount of money, find a toy.
There were bins of toys with prices as low as five
cents. One day I was in Aunt Julie’s and there was a
bin of what looked like halves of small hollow,
rubber balls (Figure 9.9a). They were called poppers.
They only cost nine cents each so I bought them all.
To play with one, you simply turn it inside out and
then put it on a flat surface. After a few moments it
pops up in the air about a meter or so. For some
reason, they’re very addictive.
The seeming simplicity of the poppers is
deceptive. They’re more complicated than you might
think. There are actually two different accelerations
that occur, one right after the other. Inverting the
popper puts potential energy into it. As it restores
itself to its original shape, the stored energy produces
a force on the table and the popper very quickly
accelerates from rest up to its takeoff speed from the
table. That final speed for the first acceleration
becomes the initial speed for the freefall acceleration
that occurs next. Your job is to work backwards from
the average maximum height of the popper to answer
a number of questions about the motion of the
popper, ultimately determining the time of the “pop.”
PURPOSE
To gain experience using the equations of motion as they apply to an accelerating
object.
PROCEDURE
Invert a toy popper onto the lab table (Figure 9.9b) and let it “pop” into the air
several times, measuring its maximum height with a ruler or rulers each time.
DATA
Figure 9.9a: Plastic
Popper
Maximum Height of
Popper (m)
Average maximum height of popper: ___________
QUESTIONS/CALCULATIONS (SHOW ALL WORK)
1.
Calculate the initial speed of the popper.
(Check this with me before you move on.)
Figure 9.9b: Inverted
Popper
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2.
Calculate how fast the popper is moving after 0.20 s.
3.
Calculate the time it takes to reach its maximum height.
4.
Calculate how far the popper has risen in 0.30 s.
5.
Let’s say that as soon as the popper popped, the table and floor disappeared. Calculate how long it would
take the popper to reach a point 5.0 m below where it started.
6.
If the inverted popper restores itself by pressing on the table through a distance of about 1.5 cm, calculate
the acceleration of the popper as it pushes against the table.
7.
Calculate the time of the pop.
Move ahead
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100% CORRECT
For each of the following questions, give clear and complete evidence for your choice in the space provided.
1. _____
A ball tossed vertically upward rises, reaches its highest point, and then falls back to its starting point.
During this time the acceleration of the ball is always
a. in the direction of motion
c. directed upward
b. opposite its velocity
d. directed downward
2. _____
At one instant an object in free fall is moving upward at 50 meters per second. One second later its speed
is about
a. 55 m/s
b. 45 m/s
c. 40 m/s
d. 35 m/s
3. _____
A rock is thrown straight upward at 30 m/s. Approximately how much later will it return to where it was
initially released?
a. 3 s
b. 6 s
c. 10 s
d. 30 s
4. _____
If you drop an object, it will accelerate at a rate of -9.8 m/s2. If you instead throw it downwards, its
acceleration (in the absence of air resistance) will be
a. less than -9.8 m/s2
b. -9.8 m/s2
c. greater than -9.8 m/s2
5. _____
A bullet is dropped into a river from a very high bridge. At the same time, another bullet is fired from a
gun, straight down towards the water. Neglecting air resistance, the acceleration just before striking the
water
a. is greater for the dropped bullet
c. is the same for each bullet
b. is greater for the fired bullet
d. depends on how high they started
6. _____
Someone standing at the edge of a cliff throws one ball straight up and another ball straight down at the
same initial speed. Neglecting air resistance, the ball to hit the ground below the cliff with the greater
speed will be
a. the one thrown upward
b. the one thrown downward
c. neither - they will both hit with the same speed
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QUESTIONS AND PROBLEMS
LINEAR MOTION (CONTINUED)
1.
In the song “The Ode to Billy Joe,” Bobbie Gentry sings about how Billy Joe Macallister and his girlfriend
are seen dropping something suspicious off the Tallahatchie Bridge (I think it was a baby). Assume this
“package” is in unrestricted freefall for 5.0 seconds and then (ouch) it hits the water.
a. What is the velocity of the “package” just before hitting the water?
b.
What is the displacement of the “package” during the fall?
2.
A United Airlines jet loses an engine and has to make an emergency landing on a little municipal runway.
It lands, touching down on the runway with a speed of 72 m/s. Once the jet touches down, it has only
350 m of runway in which to reduce its speed to 5.0 m/s (a more typical runway length is 750 m). Calculate
the average acceleration of the plane during landing and compare it to freefall acceleration.
3.
A ball is thrown straight down and accelerated by gravity. After 2.0 seconds, it is moving at 35 m/s. At
what velocity was it originally thrown?
4.
A hotshot baseball pitcher throws a baseball vertically upward. 7.20 seconds later the ball has a downward
velocity of 21.5 m/s. What was the velocity of the ball when the pitcher threw it?
5.
A car moving at 18 m/s is slowed at a rate of 1.5 m/s2. How fast is it moving after 5.0 seconds?
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6.
The image to the right is an F/A 18
Hornet about to be launched from the
deck of USS George Washington. You
can see other images of aircraft carriers at
http://www.navy.mil/navydata/ships/carri
ers/carriers.asp. During launch, the
Hornet will attain a speed of 78 m/s over
a distance of just 76 meters.
a. What acceleration is necessary for
this to happen?
b.
How much time will it take the F/A 18 Hornet to take off?
7.
Talking on his cellphone while he’s driving, a guy doesn’t see a deer run out in the road in front of him.
He’s traveling at 33 m/s and once he sees the deer, he slams on the brakes and is able to decelerate at
15 m/s2. If the deer is 35 m away when he starts braking, does he hit the deer?
8.
A mean wife wants to collect on her husband’s life insurance policy so she invites him to the observation
deck on top of a 95-story building, 427 m high. She coaxes him to look over – way over – the edge. Then
she accidentally … “bumps” him.
a. Ignoring air resistance, what is the velocity of the guy when he strikes the ground?
b. How much time does he have to think about how rotten his wife is?
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9.
The school gets a new high-dive for the pool and the star diver gives it a try, springing upward with the
initial speed of 2.2 m/s from the board (4.0 m above the water). What is his velocity when he strikes the
water?
10. Two girls with slingshots are on the top of a cliff scouting for birds. They see two, one straight up and one
straight down. One girl fires a pebble straight up with an initial speed of 15 m/s and the other fires a pebble
straight down with an initial speed of 9.0 m/s. How far apart are the two pebbles after 0.50 s?
11. Suppose a car is traveling at 25.0 m/s, and the driver sees a traffic light turn red. After 0.750 s has elapsed
(the reaction time) the driver applies the brakes, and the car decelerates at 6.80 m/s2. What is the total
stopping distance of the car from the point where the driver first notices the red light?
12. Model rockets have small engines that burn for only about 0.55 seconds. During that time, the average
acceleration of the rocket is about 100 m/s2. After the engine burns out, the rocket begins to freefall,
coasting to a much higher altitude. Assuming it is shot straight up, how high will it go and what is its total
time in the air before it hits the ground?
Move ahead
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100% CORRECT
Critical Thinking Questions
1.
2.
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