Download Study Guide for Physics Final Exam—1st semester

Study Guide for Physics Final Exam—1st semester
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Date___________________________
1.
What is a hypothesis? Give and example of a hypothesis we stated
during class this semester.
A Hypothesis is an educated guess as to why things happen. Each project
and lab activity has asked us to explain what we thing will happen in a variety
of circumstances.
2.
Measure the angle of this vector.
East is 0o, North is 90o, West is 180o and
South is 270o
This vector has an angle of about 250o
Southwest
3.
The teacher was pacing around the classroom. She started at Point A,
moved to Point B, then stopped at point C. What is her displacement
from Point A?
Displacement is the most direct distance and direction between start and
finish. Point A to Point C is about 4.5 meters southeast using the graphical
method or c2 = a2 + b2
c2 = (4)2 + (2)2
c2 = 16 + 4 = 20 Square root= 4.5
m
Point A
Point D
Point B
Point C
4. A student walks 3 km east and then 8 km north. What is her
displacement?
Displacement is the most direct distance and direction between start and
finish. Point A to Point C is about 8.5 km Northeast using the graphical
method or c2 = a2 + b2
c2 = (8)2 + (3)2
c2 = 64 + 9 = 73 Square root= 8.5
km
5. A hiker travels south along a straight path for 9 km. He then turns west
and goes 4 km. What is the hiker’s displacement?
Displacement is the most direct distance and direction between start and
finish. Point A to Point C is about 9.8 km Southwest using the graphical
method or c2 = a2 + b2
c2 = (9)2 + (4)2 c2 = 81 + 16 = 97 Square root= 9.8
km
6. Give examples of things that would be considered vector quantities.
Velocity, displacement, acceleration, forces, and momentum are all vector
quantities with both magnitude and direction.
7. What units might you use to measure the mass of a car? The mass of a
fingernail? The length of a pencil?
Kilograms for a car, grams or milligrams for a fingernail, and centimeters for the
length of a pencil.
8. Convert these numbers to standard form:
a)
6.02 x 1023 atoms = 602000000000000000000000 atoms
b)
2.3 x 10 -2 minutes = 0.023 minutes
9.8 x 10 4 km = 98000 km
c)
9. Write these numbers in scientific notation:
a)
0.0000054 minutes = 5.4 x 10-6 minutes
b)
236100000 km = 2.361 x 108 km
c)
0.048 cm = 4.8 x 10-2 cm
160
140
Distance (km)
10.
120
100
80
60
40
20
0
0
1
2
3
4
5
6
Time (hours)
What is the velocity of the car shown in the graph above?
30 km/h
How long would it take the car to travel 100 km?
About 3.3 hours
11. A rock is thrown over a cliff. Describe the rock’s velocity as it travels
toward earth.
V = at if the acceleration of gravity is 10 m/s2 then the velocity at any time period
is 10 times that time.
12. A feather and a bolt are dropped at the same time in a vacuum. Which
one will hit the ground first and why?
Both hit at the same time because all objects fall at 10 m/s2 in the absence of air
resistance.
13. A rock is thrown over a cliff. How far will it have fallen after 4.5 seconds?
How fast will it be going?
D = ½ at2
v = at
a of gravity = 10 m/s2
D = ½ (10)(4.5)2
v = (10)(4.5)
D = ½ (10) 20.25
v = 45 m/s
D = ½ 202.5
D = 101.24 m
14. A rock is thrown straight out
from a cliff. Compared to a rock
that is dropped straight down
from the same height, which
one will hit the ground first?
Explain your answer!
Both hit at the same time because all
objects fall at 10 m/s2 in the absence
of air resistance.
15. Give three examples of projectile motion.
Basketballs, cannonballs, and spitballs
16. A boy throws a ball off a 4.9 m tower.
How fast did he throw it if it landed 20
meters away?
D = ½ at2 or t2 = 2D/a = 2(4.9)/10 = 1 second
20 meters in one second is 20 m/s
17. What angle should a cannon be fired in order to get the maximum
distance?
Maximum range is always achieved by a 45o angle of launch
18. Mass X (2 kg) and mass Y (1 kg) are dropped from a tall building at the
same time. Which one will be moving faster? Why?
Both move at the same speed (v = at) because all objects fall at 10 m/s2 in the
absence of air resistance.
19. Calculate the car’s velocity using the
graph at the right.
10 m/s
20. A horse gallops a distance of 15 km in 40 minutes. What is its velocity?
V = d/t = 15/40 = 0.375 km/min
21. A dolphin swims at a speed of 1.85 km/hour. How far has the dolphin
traveled after 0.85 hours?
D = tv = (0.85)(1.85) = 1.5725 km
22. A soccer ball is kicked horizontally. What is its average speed if it traveled
25.0 meters after 4.8 seconds?
V = d/t = 25/4.8 = 5.2 m/s
23. What does the graph tell you about the car’s acceleration?
a linear slope displays a constant acceleration
7
Velocity (m/s)
6
5
4
3
2
1
24. Draw a ticker-tape diagram of an
object that is accelerating.
0
0
5
10
15
Elapsed time ( sec)
OO O O
O
O
O
Increasing distances or decreasing disatance show a change in
velocity(acceleration)
Constant velocities show even distances
O
O
O
O
O
O
O
O
O
O
25. Calculate the
car’s
acceleration
between 2-3 seconds.
A = (v2 – v1)/t
A = (6 – 4)/1 = 2 m/s2
v1 = 8/2 = 4 m/s
v2 = 18/3 = 6 m/s
26. Suppose a car is moving in a straight line and steadily increases its speed.
It moves from 45 km/h to 50 km/h in the first second and from 50 km/h to
55 km/h in the next second. What is the car’s acceleration?
A = (v2 – v1)/t
A = (50 – 45)/1 = 5 m/s2
A = (v2 – v1)/t
a = (55 – 50)/1 = 5 m/s2
27. A bicyclist accelerates at 0.8 m/s2 during a 5.0 second interval. What is
the change in velocity of the bicyclist?
V = at = (0.8)(5.0) = 4 m/s
28. Calculate the acceleration of the marble as it rolls down the ramp.
A = v/t = 2/1 =2 m/s2
29. Calculate the marble’s velocity at point B.
2 …4…. 6 …… 8 …… 10 m/s ……..
30. What is inertia? Give examples.
Inertia is an objects resistance to a change in motion(acceleration). It’s more
commonly stated as an objects tendency to stay at rest or stay in motion. It
means lazy in Italian, Freshman have a lot of inertia, so if teachers get them to
do more work now they’ll be better prepared for a successful high school
education.
31. A boy drops a ball while riding on a moving train car. Where will the ball
fall in relation to the boy? Explain your answer!
Straight down if the train is moving at a constant velocity, so is the kid and his
ball.
32. What causes an object to accelerate? Give an example.
Forces! Read the Book or you’ll be forced to repeat physics
33. An astronaut throws a 1.5 kg rock in outer space. After he throws the
rock, how much force is needed to keep the rock in motion?
Zero!! Newton Says, “An object in motion will remain in motion until an outside
force acts on it!!” It will continue in a straight line forever unless Aliens stop by to
pick it up or a wormhole sucks it into the 11th dimension.
34. Nellie weighs 200 Newtons. She is hanging on the spring scale in
various positions. What should the spring scales read in each situation?
100 N + 100 N for two strings
200 N in one string reads on both scales
35. How do you determine which object has the greatest inertia? What affects
the amount of inertia an object has?
Mass is Inertia!!
Mass in motion is Momentum!!!
36. Which string has the greatest tension? Why?
Think about It!! It’s Quite obvious, the Last one if masses are equal in all three!
37. Give examples of Newton’s 1st law. How does it work in everyday life?
Once you sit on the couch you won’t get up! So study! Study! Study!
38. If the sun’s gravity suddenly disappeared, explain what would happen to
the planets in our solar system. How and where would they move?
They would leave the system in a straight line of motion tangent to their orbits.
39. Using Newton’s Laws, explain why seat belts should always be worn..
The Law of Inertia states that an object in motion has a tendency to remain in
motion unless acted upon by an outside force. When the car stops your body
wants to smash through the windshield, but the force of the seatbelt keeps you
safe!
40. The mass of a person that weighs 500 N is about…?
Weight = mass x g g = 10 m/s2
and
mass in kg = weight /g = 500/10 m/s2 = 50 kg
41. How much force is needed to accelerate a 2 kg physics book from rest to
a speed of 6 m/s in one second? (a = 6 m/s2)
F = ma = (2)(6) = 12 N
42. What forces are acting on the ball
immediately after it leaves the boy’s
hand?
Just Gravity!!
43. Betty has a mass of 85 kg. Betty plans
to be the first woman to land on the
moon, where the gravitational pull is 1/6
as much as earth’s. What would Betty’s
mass be on the moon?
Mass is not affected by gravity it is the “STUFF” in an object. Betty has just as
much junk in her trunk on the moon as she has on Earth, so her mass is the
same!
44. A rock weighs 50 N on earth. A second rock weighs 50 N on the moon.
How do the masses of these two rocks compare?
Weight = mg
mass = weight / g
g on Earth is 10 m/s2
g on Moon is1.4 m/s2
mass earth = 50/10 = 5 kg
mass
moon = 50/1.4 = 36 kg
45. A student set up a lab as shown on the right.
What should she do if she wants to increase the
acceleration of the cart?
Increasing the Force on the cart has a direct relationship
to the Acceleration the hanging masses supply the Force
of gravity to accelerate the cart. Doubling the force
doubles the acceleration.
Increasing the mass of the cart is inversely proportional
to the acceleration, so doubling the mass of the cart is ½ the acceleration.
46.
What would the spring scale read in this situation?
100 N
Why?
47. A tow truck exerts a force of 2850 N on a car, accelerating it at 1.5 m/s 2.
What is the mass of the car?
F = ma
m = F/a = 2850/1.5 = 1900 kg
48. How much force would be needed to accelerate a 4.8 kg object to an
acceleration of 2.3 m/s2?
F = ma = 4.8 x 2.3 = 11.04 N
49. Sketch a graph showing the relationship between mass and acceleration.
Look in your book
50. Give examples of action/reaction pairs. How do the magnitude of the two
forces compare?
Always equal and opposite
51. Draw a free-body force diagram showing the forces acting on a ball that is
dropped from a tall building. Label each force.
Look in Book!
52. Draw a force diagram showing an object that is accelerating.
Look in Book!!
53. Fill in the blanks in the force diagram on the
right.
Fnormal = 80 N usually equal-opposite Weight
Fnet = 50 – 10 = 40 N
Fnet = ma a = m/F = 8/40 = 0.2 m/s2
Mass = weight/g = 80/10 = 8 kg
54. An unfortunate bug hits the windshield of a
moving truck. How does the force of the bug on
the windshield compare to the force of the windshield on the bug? Explain
Equal and opposite!!!!!!!!!!!!!!
55. In the example above, which object would accelerate more? The bug or
the windshield? Explain your answer!
F = ma Sooooooooooooooo, if
Fcar = Fbug
M A
a=m
Look in Book Newton’s Third Law
56. Give examples of objects that might have a large momentum. What
variables affect momentum?
Lots of mass and large velocity
57. A freight train rolls along a track with considerable momentum. If it were
to roll at the same speed but had twice as much mass, what would its
momentum be?
momentum = mv twice the mass is twice the momentum 2mv = 2 p
58. A truck and a Volkswagen are traveling at
45 km/ hour and then collide head-on.
Which vehicle will experience the greater
impact force? Why?
Forces are equal and opposite
59.
The brakes are slammed on a speeding truck
and it skids to a stop. If the truck were heavily loaded
so it had twice the total mass, what would the
skidding distance be?
Twice the mass is twice the distance!
Twice the speed is “22“ of four times the distance
60. Remember “walking the graph?” Sketch a distance-time graph of a
person:
i. With a velocity of zero “
(Straight line across!!! No distance change!!)
ii. Who is accelerating
(Curving upward or downward but not straight line)
iii. Who is traveling at constant velocity
Straight line slope - Up or Down
.