Transcript True or False? In the absence of air friction, the vertical component

Physics
Final Exam Review
True or False?
The horizontal component of a
projectile's velocity is
independent of the vertical
component
Answer
TRUE
• After a rock that is thrown
straight up reaches the top of
its path and is starting to fall
back down, its acceleration is
(neglecting air resistance)
__?___
Answer
• 10
which is gravity
(pulling downward)
2
m/s
A plane flying north at 50 km/h
experiences a wind 10 km/h
south. What is the magnitude
and direction of the plane?
Answer
•
This is a headwind; therefore, you
subtract.
• The answer is 40 km/h
going north
• A plane flying north at 50
km/h experiences a wind 10
km/h east. What is the
magnitude and direction of the
plane?
Answer
• Use Pythagorean Theorem
• a2 + b2 = c2
The answer is 51 km/h
northeast
• When an object is thrown in a curved path,
what is its velocity at the top of the path?
Answer
• Entirely horizontal because the vertical
component is zero
• Assuming the car starts from rest, what is
the acceleration if the car has a speed of
20 m/s for 4 s?
Answer
Unknown
a
Known
v = 20 m/s
t=4s
a = v/t
5
2
m/s
How high is a tree if an acorn falls and hits
the ground in 2.25 s?
Answer
Unknown
d
Known
t = 2.25 s
d = vot + ½
2
gt
= 0(2.25s) + ½ (10m/s2)(2.25s)2
= 0 + 5m/s2(5.0652s2)
d = 25.31 m
Question
• When a balloon deflates,
the balloon pushes on
the air and _______.
Answer
• The air pushes on the
balloon
Question
• A book weighs 10 N. When
held at rest in your hands,
the net force on the book is
____.
Answer
• Zero
Question
• As a ball falls, the action
force is the pull of Earth's
mass on the ball. What is
the reaction to this force?
Answer
• The pull of the ball’s mass
on the Earth
Question
• The outside force that
slows objects down or
stops their motion is ___.
Answer
• Friction
Question
• What is the pressure
exerted on a table by a
book that weighs 35 N and
2
covers an area of 3 m ?
Answer
Known
F = 35 N
A = 3 m2
Unknown
P
Equation
P=F
A
Solve
P = 35 N
3m2
P = 11.67 N/m2
or
11.67 Pa
Question
• A dog walks on a street.
What is the force of friction
between the 225 N dog
and the street that has a
coefficient of friction of
0.26?
Answer
Known
w = 225 N = FN
µ = 0.26
Solve
Ff = µFN
Ff = (0.26)(225N)
Unknown
Ff = ?
Ff = 58.5 N
Equation
Ff = µFN
Question
• Mass and acceleration are
__________________
proportional.
Answer
• Inversely proportional
–More mass results in less
acceleration
–Less mass results in
more acceleration
Question
• Pressure and Area are
_______________
proportional.
Answer
• Inversely proportional
–More area covered results
in less pressure
–Less area covered results
in more pressure
Question
• Which has greater tangential speed, a
horse near the outside rail of a merry-goround or a horse near the inside rail?
Answer
• The one on the outside because it has a
larger radius
____ 1.
a.
b.
c.
d.
e.
Pressure in a liquid depends on the _____.
depth of the measuring point
mass of the liquid
volume of the liquid
density of the liquid
both A and D
Answer
E
The depth and the density
Archimedes' principle says that an object is buoyed
up by a force that is equal to the _____.
a.
b.
c.
d.
e.
weight of the fluid displaced
mass of the fluid displaced
volume of the fluid displaced
mass of the object
none of the above
Answer
A
weight of the fluid displaced
• What is the difference in water
pressure between the top and
bottom of a 100-m deep well?
Answer
• At the bottom the pressure
is greater
• If you lift four loads up one step,
how much work do you do
compared to lifting two loads up
one step.
Answer
• You do twice as much work
W = Fd,
therefore, if the distance
stays the same but you lift
twice as much weight, you do
twice as much work
• What is the buoyant force of a rubber
ducky floating in water that displaces 0.05
cm3 of water. (remember the density of
water is 1 g/cm3)
Answer
Known
D = 1 g/cm3
g = 10 m/s2
V = 0.05 cm3
Unknown
Fb
Equation
Fb = DgV
Solve
Fb = DgV
=(1g/cm3)(10m/s2)(0.05cm3)
Fb = 0.5 N
• Draw a parallel and series circuit with
three resistors. Label the resistors, wire
and battery.
Answer
• Series
Parallel
wire
battery
• The Tacoma Bridge collapsed due to the
alignment of frequencies between the
bridge and the wind which is called ___.
Answer
• Resonance
• Which is the angle of reflection?
• Which is the angle of reflection?
– Angle C
• Which is the angle of reflection?
• Which is the angle of incidence?
– Angle B