Download File - PHYSICS PHUN WITH MS.BEGUM

1st Semester Physics Review 2014
For the following chapters: 2 (Mechanical Equilibrium), 3 (Newton’s 1st law of motion), 4 (Linear Motion), 5 (Projectile
Motion), 6 (Newton’s 2nd law of motion), 7 (Newton’s 3rd law of motion), 8 (Momentum), 9 (Energy), 10 (Circular
Motion), 17 (The atomic Nature of Matter), 18 (Solids): Study Notes, Vocabulary Definition, use Chapter quizzes to
review all chapter questions, review all handouts, worksheets, problem ws, consult online videos (YouTube & khan
academy), online interactive quiz, other weblinks to help clarify misconceptions.
1. The rate at which velocity changes with time is called acceleration.
2. Even if you are turning at a constant speed, you are accelerating because you are changing direction.
3. The acceleration of a car traveling in a straight line at a constant speed is 0 m/s2
4. An object moving in a straight line & steadily increases its speed: from 10 km/h to 20 km/h, then 20 km/h to 30 km/h,
then 30 km/h to 40 km/h each second: its acceleration is 10 km/ h s
5. For a freely falling object dropped from rest, its velocity is v = gt
6. For a freely falling object dropped from rest, its velocity increases but its acceleration does not. Acceleration is
constant: 10 m/s2
7. Free fall is due to gravitational pull which does not change, therefore; acceleration due to gravity (g) does not change
and is a constant: 10 m/s2
8. When an object falls freely, the distance it falls each second increases and is calculated by d= ½ gt2
9. An object is tossed upwards, what is the change in velocity each second on the way up? On the way down?
10. Velocity changes at top because although speed is not changing, but direction is.
11. An object thrown straight up returns to same height moving at same velocity
12. Mass does not affect motion in a free fall, falls at rate of 10 m/s each second.
13. Once an object is set in motion, no other force is necessary to keep it in motion.
14. When any two objects touch or collide with each other, the force each exerts is the same.
15. Quantities that have both size (magnitude) and direction are called vectors. Quantities with only size (magnitude) are
called scalar.
16. When all of the forces on an object equal zero, the object is in equilibrium. It can be stationary or moving at a
constant velocity.
17. The Earth and sun pull on each other with equal force.
18. When the Earth’s shadow falls on the Moon, this is called a Lunar Eclipse.
19. A single vector can be replaced by two vectors in the X and Y direction. These vectors are called the components of
the original vector.
20. The horizontal component is independent of vertical component
21. Velocity is an example of a vector. Acceleration is a vector quantity. Force is a vector quantity. Displacement is a
vector quantity.
22. Vector quantity is represented by an arrow, whose length is drawn to scale & represents the magnitude and
direction indicates the direction of motion.
23. For a projectile, the horizontal component is constant as it moves through the air. Due to a lack of horizontal force
acting on it (constant vx & dx)
24. For a projectile, the vertical component’s motion is similar to free fall
25. The horizontal component of a projectile’s velocity doesn’t change as the projectile moves
26. With no air friction, the vertical component of a projectiles velocity changes by 10 m/s each second.
27. A ball is thrown into the air at some angle, at the top of the ball’s path, its velocity is all horizontal.
28. A cannonball will fall how far below its initial straight-line path after t seconds?
29. A projectile has minimum speed at its top of its path.
30. A bullet is fired from a gun & dropped from the same height at the same moment. They will both his the ground at
the same time. Distance fallen during projectile motion (dy) & free fall are the same.
31. Projectiles launched at complimentary angles will land at the same dx (horizontal downrange distance)
32. An airplane that encounters a crosswind will have its velocity increased and move at an angle.
33. An upwardly launched projectile: vertical acceleration is 10 m/s2, horizontal acceleration is 0 m/s2
34. An object dropped from a moving vehicle will have the same vx as the moving vehicle.
35. Upwardly launched projectiles: 45 ° yields farthest downrange, dx and 90 degrees yields farthest dy.
36. After a rocket is fired into frictionless outer space, no force is needed to keep it going.
37. The amount of matter in an object is called its mass. Mass is directly proportional to inertia.
38. The metric unit of force is called the Newton.
39. Objects keep moving, even when there are no forces present due to their inertia.
40. Inertia is the resistance of any material to change its state of motion.
41. A car at rest has more inertia than a mouse moving at 20 m/s, because it has more mass. Mass is a measure of
inertia.
42. If the forces acting upon an object are balance, then the object could be moving at a constant velocity or at rest (not
accelerating).
43. The acceleration of an object is directly proportional to the net force acting upon it. It moves in the same direction as
that net force.
44. Air resistance is caused by friction between the air and an object moving through the air.
45. Friction acts in a direction that opposes the motion of an object, is caused by irregularities between the surfaces, is
parallel to the surface in contact.
46. An object on the Earth and on the moon have the same mass but different weights. Objects in outer space have no
weight due to the lack of gravitational force.
47. The net force acting on an object at equilibrium is 0N. Therefore, not horizontal forces acting upon it.
48. The object could be at rest or moving at a constant velocity.48. The law of inertia pertains to both moving objects
and objects at rest.
49. If you are hanging from a bar by both arms and you let go and hang by one arm. The tension force now in your one
arm is Doubled compared to the tension force in both arms
50. Pressure is defined as force per area.
51. Whenever one object exerts a force on another, an equal & opposite force is exerted by the 2nd object
52. A net force will cause acceleration and the acceleration will be in the same direction as the net force.
53. Acceleration is directly proportional to the net force
54. Acceleration is inversely proportional to the mass of an object.
55. A support force acts on all objects on a surface that is equal in magnitude and opposite in direction to the object’s
weight.
56. If a bicycle and a car have a head on collision, the force on each is the same.
57. A rocket ship is pushed forward by the gases that are pushed out of the back of the ship. Rocket pushes exhaust
backwards, and exhaust pushes rocket forward.
58. The Earth and Moon pull on each other with equal force. You and the Earth pull on each other with equal force.
59. If the external force on a system is equal to zero, there can’t be a change in momentum. There can be momentum
present if the object is already moving,
60. Impulses are larger when bouncing takes place.
61. The metric unit of length is called the meter.
62. When a ball is thrown into the air, at its highest point it has zero velocity and acceleration down.
63. Speed is distance covered per unit of time.
64. Possible speed units are miles per hour, kilometer per hour, meters per second, light years per century
65. A car’s speedometer can show you instantaneous speed.
66. Acceleration is change in velocity per unit of time.
67. A resultant is what you get when you add two or more vectors. When adding a 7 m and 2 m vector the maximum
resultant is 9 m, the minimum is 5 m. Using a2 + b2 = c2 you can get the resultant if the vectors are at right angles.
68. An airplane flying into a head wind loses ground speed, and an airplane flying with the wind gains ground speed. If
an airplane flies at right angles to the wind, then the ground speed increases. (The hypotenuse of the triangle is bigger
than the two vectors.)
69. All freely thrown objects in the air are considered projectiles.
70. A kilogram of iron and a kilogram of Styrofoam have the same mass.
71. The acceleration of an object is directly proportional to the net force acting on it. (F = ma)
72. If the force on an object doubles, the acceleration then doubles.73. You would exert the most pressure on the
ground with a shoe having the smallest area. Women in high heels exert the most pressure.
74. Any time you hit something there is an equal force on both objects.
75. A 600.0 N person causes the floor to push back with 600.0 N.
76. Forces always occur in pairs and occur simultaneously. They are = in magnitude and opposite in direction.
77. A softball player catches a ball. If the action force is the force the ball exerts backwards against her glove, then what
is the reaction force in this interaction?
78. As a rock falls toward the Earth, suppose that the action force is the pull of the Earth downward on the rock, then
what is the reaction force?
79. What is the interaction pair that causes a car to move along a road, or you to walk?
80. What is the interaction pair that enables a rocket to move in outer space?
81. If an object is not moving (zero velocity) then it has no momentum.
82. Momentum is mass x velocity. A large object moving fast has more momentum than a small object moving slowly.
83. Momentum changes for an object are equal to the impulses acting upon it.
84. Momentum is a measure of how difficult it is to stop a moving object.
85. Impulses are force times time. The biggest impulse would involve a large force for a long period of time.
86. Momentum equals mass times velocity. If either are doubled then so is momentum. if both are doubled then
momentum is quadrupled.
87. If mass remains the same and momentum changes, then a force act upon object that changed the velocity and
therefore, the object is accelerating.
88. Impulse is the product of force times time. If either are doubled then impulse is doubled.
89. Impulse causes a change in momentum; therefore, impulse = change in momentum.
90. Can increase momentum of a golf ball by increasing the force acting on golf ball by swinging harder. Or you can
increase time of impact by following through with your swing.
91. When the total momentum before a collision equals the total momentum after a collision, momentum is said to be
conserved.
92. When you throw a ball you experience an equal and opposite force to the one you give to the ball; therefore, you
experience an impulse.
93. If you keep the force constant but double the time of impact then the impulse is doubled. (if impulse is doubled then
so is the change in momentum)
94. When a dish falls the impulse will be the same whether it lands on a hard wood floor or carpeting. However the force
of impact will be lower on the carpeting due to the time of impact being increased.95. For the same change in
momentum: if the time of impact is increased then the force of impact must decrease.
96. If a net force acts on you, your momentum will change. A force exerted over a period of time is an impulse that
causes a change in momentum.
97. Impulses are doubled for bouncing
98. If 2 eggs are of equal mass and are thrown at the same velocity at a wall and a bed sheet, they will have the same __.
The wall and the sheet both apply equal __. The wall applies a __ force over a __ time, while the sheet applies a __force
over a __ time.
99. Possible units for a rotational speed are revolution per second, revolutions per hour, and rotations per minute. Hertz
is rotations per second. Frequency is rotational velocity.
100. The direction of any centripetal force is toward the center of the circle.
101. If you whirl a tin can on the end of a string and the string suddenly breaks, the can will fly off, tangent to its circular
path.
102. The fastest part of a spinning wheel is on the outside edge.
103. The outside rim of a wheel has a greater linear speed than parts near the center.
104. Any force that causes an object to move in a circular path is called a centripetal force.
105. When you whirl a can on the end of a string, the centripetal force is actually the pull of the string on the can.
106. On a merry-go-round the outer horse and inner horse both have the same frequency which is= to the rotational
velocity.
107. On a merry-go-round the outer horse is 4 times farther from the axis of rotation than the inner horse. The
tangential speed of the outer horse is is 4 times that of the inner horse.
108. When a car makes a turn, the seat belts provide centripetal force; the inward force that causes you to continue in
the circular path.
109. Tangential speed is directly related to rotational speed and radius.
110. The rotation of the earth causes night and day.
111. The revolution of the earth along with tilt on its axis, causes seasons
112. The equator has the greatest tangential velocity.
113. All locations on Earth have the same rotational speed (frequency)
114. There are 4 time zones in the continental United States. Eastern, Central, Mountain, and Pacific. Each one is 1 hour
behind the previous zone.
115. The period of the earth’s rotation is 24 hours and the period of the earth’s revolution is 365 days.
116. The friction between the road and the tires cause the centripetal force that keeps the car on its circular path.117.
Water flies out tangent to the circular spinning tub due to a lack of force. The clothes continue to spin because the tub
exerts a centripetal force on the clothes keeping them in a circular motion.
118. Work is the product of force and distance
119. Power is the rate at which work is done
120. Mechanical energy consists of two forms: Kinetic energy and potential energy
121. Potential energy is energy due to its position
122. Kinetic energy is energy of motion
123. The work done to lift an object = its gravitational potential energy
124. Energy is the property of an object to do work
125. Gravitational potential energy relies on dy (vertical distance) and the mass (not the path taken)
126. Law of conservation of energy states energy can never be created or destroyed but it can be transformed from one
form to another
127. A job done slowly and a job done quickly: both require the same amount of work/energy but different amounts of
power (due to time)
128. Which requires more work: lifting a 50kg box vertically 2 meters or lifting a 25kg box vertically 4meters
129. A car has 2000 J of KE, if the car’s velocity doubles … what is it KE now?
130. A 2 kg arrow is pulled back in a bow and possesses 70J of PE. How much KE will the arrow possess just after it has
been shot?
131. What power is expended to lift a 100N box 5 meters in 2 seconds?
132. What is the SI unit for energy, KE, PE, Work, Power?
133. How much KE does a 2 kg toy car possess if it is moving at 3 m/s?
134. Explain figure 8.7 and 8.8 using the law of conservation of energy
135. If a forklift is replaced with a new forklift that has twice the power, how much greater a load can it lift in the same
amount of time? if it lifts the same load, how much faster can it operate?
136. How much work is done on a 100N box you carry horizontally across an 8 meter room? None
137. If the velocity of a car doubles, how does the KE change?
138. If the velocity of a car triples how does the KE change?
139. Work is needed to lift an object, how many times more work is required to lift the object three times as high?
140. If a car traveling at 60 km/h will skid 20 m when its brakes lock, then how far will it skid if it is traveling at 120 km/h
when its brakes lock?
141. Does an object with momentum always have energy? Does an object with energy always have momentum?
Practice Problems for 1st Semester Exam
1. How far would you travel if you maintain a velocity of 10 m/s for 30 s?
2. Jay is driving a go-kart at 30 m/s. He slams on the brakes and comes to a stop in 3s. What was the acceleration of Jay
go-kart?
3. While on a rollercoaster at Busch Gardens, Katie’s sandal falls off.
a) If there were no air resistance, what would be the velocity of the sandal after falling for 5.5 seconds? b) How far
would the sandal fall during this time?
4. You drop an egg from the bleachers that are 9.5m high.
a) What will be the reading on a stop watch after recording the elapsed time of the egg’s fall?
be the velocity of the egg just before it hits the ground?
b.) What will
5. Sarah is flying an airplane north at 100km/ h and has an easterly crosswind of 50 km/ h. What is the resulting velocity
of her plane?
6. Kiersten, a Pinellas county sheriff is trying to determine the speed of a car that went off the Howard Franklin Bridge
on a rainy night and landed in the water 5 m below. The car landed 10 m horizontally from the bridge in the water. How
fast was the car going when it left the road?
7. Mrs. Begum’s class is trying to calculate where a flour sack would land if dropped from a moving airplane. The plane
would be moving horizontally at a constant speed of 50 m/ s at an altitude of 200m. Neglecting air resistance, how far
horizontally from the dropping point would they predict the flour sack would land?
8. A pull of 6N causes a 0.5 kg object to move at a constant velocity. Complete the following.
9. An applied force of 30N is used to accelerate an object with a weight of 80N to the right across a frictional (with
friction) surface. The object encounters 10N of friction
10. A rightward force of 25N is applied to a 5kg object to move it across a rough surface with a rightward acceleration of
2 m/s2
Complete the following. Use this diagram for #8-10
11. What is the acceleration of a 2000 kg airplane just before takeoff when the thrust of its engine is 500N?
12. A net force of 150N causes a mass to accelerate at the rate of 5 m/s2. What is the mass?
13. a. What is the momentum of a 55 kg carton that slides at 4 m/ s across an icy surface?
b. The sliding carton skids onto a rough surface and stops in 4 s. What is the change in momentum of the carton?
c. What was the impulse that changed the momentum of the carton, thus
d. Calculate the force of friction the carton encountered in order to stop it in 4 s.14. a. What impulse occurs when an
average force of 20 N is exerted on a cart for 5 s?
e. What change in momentum does the cart undergo?
15. a. If Bailey rolls a 5 kg bowling ball into a pillow at 3 m/s and the ball stops its motion in .5 s, calculate the force
which the bowling ball exerted on the pillow.
b. What force does the pillow exert on the ball?
16. Hamlet, a hamster, runs on his exercise wheel, which turns around once every 3.5 s. What is the frequency and
period of the wheel?
17. Sam’s favorite ride at Busch Gardens is the rotor, which has a radius of 4 m. The ride takes 2 seconds to make one
full revolution. Sam’s mass is 60 kg.
a. What is Sam’s frequency?
b. What is the period of Sam’s circular motion?
c. What is Sam’s rotational velocity?
d. What is Sam’s tangential velocity?
e. What is Sam’s centripetal acceleration?
f. What is the centripetal force that is exerted on Sam to maintain his circular motion?
g. What is the centrifugal force exerted on Sam?
18. Andie twirls a round piece of pizza dough overhead. It revolves .25 times in one second. A 0.02 kg piece of pepperoni
is stuck on the dough 0.13 m from the pizza’s center.
a.) What is the frequency of the pepperoni?
b.) What is the pepperoni’s period?
c) What is the pepperoni’s tangential speed?
d) What is the pepperoni’s centripetal acceleration?
e) What is the centripetal force on the pepperoni?
19. a. How much work is done on a 5 kg backpack filled with books that you carry up a flight of stairs that is 4 meters
high?
b. What is the PE of the backpack when it is lifted to this height?
c. What power is expended if you lift the backpack to the top of the stairs in 4 seconds?
d. How could you double your power?
20. A 20 kilogram go-kart can move at a velocity of 3 m/s. What is its KE?
FORMULA BANK (Reference)
Speed = distance/time
Centripetal Force Fc = mv2/r
Velocity = distance/time
Power = Work/ time
Momentum = mass X velocity
Kinetic energy = ½ mv2
Force = mass X acceleration
Distance in free fall = ½ gt2
Potential Energy = mgh
Velocity- Freefall = gt
Work = Force X distance
Pressure = Force/area
Tangential Speed = radial distance X rotational speed
Impulse = Ft = ∆ (mv)
Acceleration = change in velocity/ time or Vf-Vi/t or ∆V/t
Efficiency = useful work output/ total work input or actual mechanical advantage/ theoretical mechanical advantage
Mechanical Advantage = Input Distance/ Output Distance or Output force/ input force
Weight = mass X acceleration due to gravity (Remember g on earth is 10 m/s2)