A. greater than the potential energy
B. less than the potential energy
C. equal to the potential energy
D. cannot be known
Ans: B. less than the potential energy
-As an object falls from rest, its gravitational potential energy
is converted to kinetic energy. The initial potential is equal to the maximum
kinetic energy. Since the object, hits the surface of the Earth, its kinetic
energy is converted back to potential energy. Therefore, KE= O and PE= 100 J.
2. What happens to the kinetic energy of an object if tit’s
speed is doubled?
A. It will be halved.
B. It will be doubled.
C. It will be tripled.
D. It will be quadrupled.
Ans: D. It will be quadrupled.
-Since the formula for kinetic energy is KE=mv2/2, if
the speed is doubled, then the KE would be quadrupled due to the square of the
velocity in the equation.
3. What is the type of energy possessed by a simple pendulum
when it is at the mean position?
A. Kinetic energy
B. Mechanical energy
C. Potential energy
D. Sound energy
Ans: A. Kinetic energy
- The potential energy is maximum at extreme position. Kinetic
energy possessed by the pendulum bob is maximum at the mean position.
4. A ball is thrown upward into the air with a speed that is
greater than terminal speed. On the way up, it slows down and after its speed
equal the terminal speed but before it gets to the trajectory_____.
A. it speed up
B. its speed is constant
C. it continues to the slow down
D. its motion becomes jerky
Ans: C. it continues to the slow down
-Once a ball is thrown upward, the primary force acting on it is
gravity, which produces a downward acceleration. Every second, there is a
change in velocity of approximately 10 m/s. This change in velocity is directed
downward, however, opposite to the direction of the original velocity. It subtracts
from the original velocity rather than adding to it.
no5. When a bullet is fired from a riffle, the force in the riffle
is equal to the force on the bullet. Why is it that the energy of the bullet is
greater than the energy of the recoiling rifle?
A. Because there is more impulse on the bullet
B. Because the force on the bullet acts for a longer time
C. Because the force on the bullet acts for the longer distance
D. Because the bullet’s momentum is greater than that of the rifle
Ans: C. Because the force on the bullet acts for the longer
distance
-A moving object has momentum, which is the product of its mass
and its velocity. The faster something moves and the heavier it is, the more
momentum it has. Even though bullets are small compared to the rifle, they have
lots of momentum because they go so fast resulting to great amount of kinetic
energy.
6. Car A has a mass of 1000 kg and the speed of 60 kph while car
B has a mass of 200 kg running at a speed of 30 kph. What is the kinetic energy
of car A?
A. Half that of car B
B. Equal that of car B
C. Twice that of car B
D. Four times that of car B
Ans: C. Twice that of car B
-Car A and Car B
60 kph = 16.67 m/s 30 kph = 8.33 m/s
KE=mv2 KE=mv2
2 2
=(1000 kg) (16.67 m/s)2 =(2000 kg) (8.33 m/s)2
2
2
=138 944.45 J=69 388.90 J
7. An object is thrown straight up. Which of the following is
TRUE about the sign of work done by the gravitational force while the object
moves up and down?
A. Work is zero on the way up, work is zero on the way down.
B. Work is negative on the way up, work is negative on the way
down.
C. Work is negative on the way up, work is positive on the way
down.
D. Work is positive in the way up, work is negative on the way
down.
Ans: C. Work is negative on the way up, work is positive on the
way down.
-Work can either be positive or negative. If the force has a
component in the same direction as the displacement of the object, the force is
doing positive work, if otherwise, the force does negative work.
8. What happens to the kinetic energy of a moving object if the
net work done is positive?
A. The kinetic energy remains the same.
B. The kinetic energy increases.
C. The kinetic energy decreases.
D. The kinetic energy is zero.
Ans: B. The kinetic energy increases.
-If an object’s speed increases, then the work done on the body is
positive and its kinetic energy has increased. Whereas, if the object’s speed
decreases, then its kinetic energy decreases and the change in kinetic energy
is negative.
9. Object A with a mass of 4 kg is lifted vertically 3 m from
the ground, object B with a mass of 2 kg is lifted 6 m up. Which of the
following statement/s is/are TRUE?
I. Object A has greater potential energy since it
is heavier.
II. Object B has greater potential energy since it
is lifted to a higher position.
III. Two objects have the same potential energy.
A. I only
B. II only
C. III only
D. not enough information given
Ans: C. III only
-Object A Object B
PE = mgh
PE = mgh
PE = (4kg) (9.8m/s2) (3m) PE = (2kg) (9.8m/s2)
(6m)
PE = 117.60 j PE = 117.60 J
10. According to the scientific definition of work, pushing a
table accomplishes no work unless there is __________.
A. an opposing force
B. a net force greater than zero
C. an applied force greater than its weight
D. movement in the same direction as the force
Ans: D. movement in the same direction as the force
-In physics, a force is said to work, if when acting on a body,
there is a displacement of the point of application in the direction of the
force
11. A machine does 2 500 J of work in one minute. What is the
power developed by the machine?
A. 21 W
B. 42W
C. 2 500 W
D. 150 000 W
Ans: B. 42W
-P = W= 2500
J = 42 W
t 60s
12. To which type of simple machine does a pencil sharpener
belong?
A. Inclined plane
B. Lever
C. Pulley
D. Wheel and axel
Ans: D. Wheel and axel
-Pencil sharpener actually consists of two simple machines: wedge
and wheel and axle. The blade that shaves the wood and lead from a pencil to make a sharp point is a
wedge. The hand crank of the sharpener is the axle that turns a wheel that is
attached to the gears inside the sharpener to sharpen the pencil.
13. Which of Newton’s law best explains why motorists should
always wear seat belts?
A. Law of Inertia
B. Law of Acceleration
C. Law of Interaction
D. Law of Gravitation
Ans: A. Law of Inertia
-A body in motion such as a moving car tends to stay in motion due
to inertia. In a car crash, while the car is decelerating, rapidly, your own
inertia will cause you to continue at your previous velocity. The set belt
helps overcome your inertia by slowing you down at a similar rate than the car.
14. The same net force is applied to object 1 and object 2. The
observed acceleration of the two objects are not the same; object 1 has
acceleration three times that of object 2. Which of the following is correct?
A. Object 1 has more friction than object 2.
B. Object 1 has one-third the mass of object 2.
C. Object 1 has three times the mass of object 2.
D. Object 1 has a different, less streamlined shaped than object
2.
Ans: B. Object 1 has one-third the mass of object 2.
-Since F=ma, if two objects have the same net force, and object 1
has an acceleration thrice that of object 2, it follows that it has one-third
the mass of object 2.
15. The law of inertia applies to _______.
A. moving objects
B. objects that are not moving
C. both moving and non-moving objects
D. none of these
Ans: C. both moving and non-moving objects
-Law of inertia states that a body at rest will remain at rest and
a body in motion will continue to move along a straight line unless acted by an
outside force.
16. Which statement is CORRECT about the Law of Conversation of
Energy?
A. The total amount of energy is constant.
B. Energy cannot be used faster than it is created.
C. The supply of energy is limited so we must conserve.
D. Energy must be conserved and you are breaking a law if you
waste energy.
Ans: A. The total amount of energy is constant.
-The Law of Conservation of energy states that the total amount of
energy in an isolated system remains constant over time. A consequence of this
law is that energy can neither be created nor destroyed, it can only be
transformed from one form to another.
17. Which of the following can transform electrical energy to
mechanical energy?
A. Electric bulb
B. Electric fan
C. Loud speaker
D. Television
Ans: B. Electric fan
- When you plug an electric fan to a power outlet, electrical
energy is transformed into chemical energy as the blades of the fan move.
Mechanical energy is the energy due an object’s motion or position.
18. Celso is making a picture frame. He sticks a nail into a
piece of wood and hits the nail with a hammer. Which form of energy is NOT
released when the hammer hits the nail?
A. Chemical
B. Kinetic
C. Sound
D. Thermal
Ans: A. Chemical
A raised hammer has potential energy due to its position above the
ground. When the hammer comes down and strikes the head of the nail, the
potential energy is transformed in to kinetic energy. Sound is also heard as
the hammer strikes a nail. If Celso continues to hit the nail to secure it, the
kinetic energy of the hammer is transferred to the molecules of the material of
the nail. The heat content of the body is the total energy that the body
possesses. Therefore, thermal energy content of the nail increases. Chemical
energy is not involved in this process.
19. Butch throws a baseball into the air. It rises, stops when it
reaches its greatest height, and the falls back to the ground. At what point is
kinetic energy initially converted to potential energy?
A. When the baseball is rising
B. When the baseball is falling
C. Just after the baseball hits the ground
D. While the baseball is stopped in the air
Ans: A. When the baseball is rising
-There is potential energy when the baseball is at rest. As it
rises, its potential energy is converted to kinetic energy. When the baseball
stopped in the air, KE is converted back to PE. When the baseball stopped in
the air , KE is converted back to PE. When the baseball is falling, PE is
transformed into KE. When the baseball hits the ground, KE is converted to PE.
20. Which energy conversation takes place when a toaster is
switched on?
A. Chemical to sound
B. Chemical to thermal
C. Electrical to sound
D. Electrical to thermal
Ans: D. Electrical to thermal
-A toaster usually takes in electrical energy. All of the input
electrical energy is transformed into thermal energy.
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