Kinematics Test Review Key
1.
An operational definition is … LOOK IT UP on page 11 of your lab manual.
2.
An operational definition for uniform motion is: Measure the time it takes an object to
pass through equal length segments. If the times are the same, the motion is
uniform.
3.
Be prepared to write an operational definition for some physical quantity familiar to you
that you have written an operational definition for previously. Try for example, density.
Use a balance to measure the mass of an object. Measure its volume by
displacement. Calculate density by dividing mass by volume.
4.
Take the sheet of graphs that we did car motions for and for each one write out what
motion is required. Page 31 of your lab manual (starting at the top and going across,
then down to the next row)
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
k.
l.
m.
n.
o.
p.
q.
r.
s.
t.
u.
The object is not moving and is to the right of the origin.
The object is to the left of the origin initially and moving to the right at a
constant speed.
The object is to the right of the origin initially and moving to the left at a
constant speed.
The object starts at the origin and moves to the right at increasing speeds.
The object is initially to the right of the origin. It moves to the right at a
constant speed. Then, it stops. Then, it begins moving left very fast. It then
slows and stops at the origin.
The object is to the right of the origin and is accelerating to the left.
The object begins at the origin. It moves right at a decreasing speed. It
stops, turns around and starts traveling left at an increasing speed.
The object is initially to the right of the origin. It begins moving left at a
decreasing speed. It passes the origin and slows to a stop.
The object is moving to the right, slowing, and stopping. It then turns
around and moves left, passes the origin, slows, and stops. It then turns
right and does the same thing. A pendulum has this motion.
The object is not moving.
The object is moving right at an increasing speed.
The object is moving right at a decreasing speed, it stops momentarily, and
then travels left at an increasing speed.
The object is moving left at a decreasing speed, it stops momentarily, and
then travels right at an increasing speed.
The object is moving right at an increasing speed. The acceleration stops
and it continues traveling right at a continuous speed.
The object is traveling right at a constant speed and then slows to a stop.
The object is traveling left at an increasing speed.
The object is traveling left at a decreasing speed. It then momentarily stops,
and travels right at an increasing speed with non-uniform acceleration.
It moves to the right at a constant speed, then left with a constant speed.
It moves to the left at a constant speed, then right with a constant speed.
It travels to the right and non-uniformly decelerates to zero.
It travels to the left uniformly accelerating, then uniformly decelerates, still
traveling left.
5.
A runner with a good awareness of her pace runs along a path of unknown length at a
speed of 0.20 mi/min and then walks back to her starting point at a speed of 0.05 mi/min.
She neglects to note her time for each part of her path, but she does measure the total
round trip time to be 50.0 min. How far has she run?
∆x
0.20mi / min
∆x
∆t2 =
0.05mi / min
∆t1 =
∆tTOTAL = ∆t1 + ∆t2 = 50 min =
∆x
∆x
+
0.20mi / min 0.05mi / min
50 min = (25min/ mi)∆x
∆x = 2.0miles
6.
Two sprinters run a 100. meter dash, with the winner finishing in 10.0 sec. If the other
runner was 1.00 m behind the winner at the finish, how long did it take her to run the 100
m.
The loser had only run 99 m when the winner run in 10 sec, so
∆x
99m
vloser =
=
= 9.9m / s
∆t 10.0sec
So, her total time would be
∆x
100m
∆t =
=
= 10.1sec.
v
9.9m / s
7.
The cheetah is the fastest land animal, able to reach quickly a maximum speed of 30 m/s.
But it is able to maintain this speed for only about 10s. Suppose that the cheetah stalks a
prey that has a maximum speed of 25 m/s, but is able to maintain this speed for much
longer than 10s. If it is to catch its prey, what is the maximum distance the cheetah can
be from the prey when the chase begins (neglect acceleration).
The cheetah can run (30m/s)*(10sec) = 300 m in 10 sec. The prey traveling at 25 m/s
can travel 250 m. The cheetah can’t be any further away than 300m-250m which is
50 m.
8.
Explain the difference between time and duration, position and displacement. LOOK IT
UP on page 25-28 of your lab manual.
9.
If someone is running down the x axis, what does a positive displacement mean?
Running Right
10.
If someone is running down the x axis, what does a negative displacement mean?
Running Left
11.
If someone is running down the x axis, what does a positive velocity mean?
Running Right
12.
If someone is running down the x axis, what does a negative velocity mean?
Running Left
13.
Dr Kline was getting to throw out the first pitch at the very first Lakota East baseball
game. However, there seems to be something wrong with the ball. Little did she know
that someone had slipped her a ball made of super ball material. Dr Kline and the East
catcher were separated by a distance of 10 meters. The catcher, thinking Dr Kline was
never going to throw the ball, began walking toward Dr Kline the instant she threw the
ball. The ball bounced off the catcher glove back to Dr Kline, bounced off Dr Kline back
to the catcher's mitt, and so on until the catcher reached Dr Kline and the ball was
trapped between the two. If the catcher walked toward Dr Kline at a rate of 1 m/sec and
the ball traveled at a speed of 14 m/sec, what was the total distance the ball traveled back
and forth before being trapped?
It takes the catcher 10 seconds to reach Dr. Kline, if he walks 10 meters at a rate of
1 m/s. If the ball travels for 10 seconds at 140 m/s, it travels 140 meters during that
time period.
14.
Two towns, A and B, are 200 miles apart. Car 1 starts from town A and, at the same
time, car 2 starts from town B. They move toward each other with constant speeds: car 1
at 50 mph, car 2 at 40 mph. Where do the cars meet? How long does it take for them to
meet?
x1 = 0 + 50∆t
x2 = 200 − 40∆t
When they meet they have the same x coodinate, so:
x1 = x 2
0 + 50∆t = 200 − 40∆t
∆t = 2.22hours
x1 = x = 111mi from the Town A
15.
If the distance an object traveled is plotted on a graph vs. time, what physical quantity
does that slope represent? LOOK IT UP in your notes!
16.
If the distance two objects traveled is plotted on a graph vs. time, how could you tell
which object is moving faster? LOOK IT UP in your notes!
17.
How does the distance vs. time graph of an object that is accelerating compare to the
distance vs. time graph of an object that is undergoing uniform motion? LOOK IT UP in
your notes!
18.
Find the horizontal and vertical component of a velocity vector of 50.0 m/s, 35.0˚.
vx = 50m / s cos 35 = 41.0m / s
v y = 50m / s sin 35 = 28.7 m / s
19.
Find the horizontal and vertical velocity of an object that moves from (5.00 m, 3.50 m) to
(-2.00m, 4.00m) in 2.50 seconds.
∆x −2.00 − 5.00
=
= −2.80m / s
∆t
2.50sec
∆y 4.00 − 3.50
=
= 0.200m / s
vy =
∆t
2.50 sec
vx =
20.
Find the magnitude and direction of the velocity in the previous problem.
v = vx2 + v y2 = (−2.8m / s ) 2 + (0.200m / s ) 2 = 2.81m / s
 .200 
 + 180 = −4.09 + 180 = 176
 −2.80 
θ = tan −1 