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ME217_Chptr2_Energy Principals Flashcards | StudBud
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ME217_Chptr2_Energy Principals
ME217_Chptr2_Energy Principals
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1
Equal forces are applied to a Chevy truck and a Volkswagen Beetle. The Beetle would have larger acceleration because
it has more mass.
it has less mass.
it is less expensive.
German engineers design better cars.
2
From the stand point of different systems of units, a meter is to a foot as a newton is to a
Gram
Yard
Kilogram
Pound
3
Newton’s first law: an object in motion remains in motion at constant speed unless acted upon by external force, so
an auto traveling at constant speed must use energy to overcome gravity
none of the first four selections are correct.
an auto must use energy, on a straight, level road, to overcome friction
Newton’s first law does not hold for automobiles on Earth’s surface.
4
From the basic idea of kinetic energy, we expect the kinetic energy of a car to
increase as the mass of the car decreases.
not depend on the mass of the car.
increase if either or both the mass and speed increases.
decrease as the speed of the car increases.
5
If the brakes are applied in a moving automobile, the work done by the brakes is
converted to potential energy.
negative, because the braking force applied and the motion are opposite
positive because the braking force and motion are in the same direction.
none of the previous four selections are correct.
6
The work-energy principle in physics states that
the net work done on an object equals the change in its kinetic energy.
force equals mass times acceleration.
work is a capacity for expending energy.
work and energy mean exactly the same thing
7
Car A mass is 1000 kg and speed 60 km/hr. Car B mass is 4000 kg and speed 30 km/hr. The kinetic energy of car B is_____
equal the kinetic energy of car A.
twice the kinetic energy of car A.
four times the kinetic energy of car A.
half the kinetic energy of car A.
8
In this energy converter, the laws of physics allow you to say the energy input is _____ joule and the efficiency is____
1000, 100%
1500, 50%
500, 100%
1000, 50%
9
If the net work on a car is positive, we know
there is no change in kinetic energy.
there is no net force on the car.
its kinetic energy decreases.
its kinetic energy increases.
10
A car is traveling due west, to slow down, the force on the car must be directed ______ and the work done by force is __
west, negative
west, positive
east, negative
east, positive
11
A car travels in a circle while its speedometer shows 30km/hour. Which of the following statements is true?
The velocity of the car points inside the circle.
The acceleration of the car is zero because the speed is constant.
The velocity of the car is constant.
The acceleration acting on the car points inside the circle.
12
Same net forces acted on two identical cars. Car A travels 10 m and car B travels 40 m. Kinetic energy of car A is ___
four times the kinetic energy of car B.
equal to the kinetic energy of car B.
Two time the kinetic energy of car B.
one quarter the kinetic energy of car B.
13
In physics, work is defined as
the energy of a moving object.
the force acted on a moving object.
the exchange of energy intermediated by a force acting on a moving object.
the product of mass and acceleration.
14
If conversion of energy in a certain system involves three energy conversion steps with 80% efficiency each.
The overall efficiency is the geometric mean, which is 57%
The overall efficiency is 80%
The overall efficiency is 240%
The overall efficiency is 51.2%
15
A student jumps from the floor to the top of the lecture table. A person in the audience might be heard to say correctly
the potential energy of the student has increased.
all the previous statements are reasonable.
the floor pushed up on the student.
the force of gravity has done work on the student.
16
The difference between power and energy is
power is given by work, while energy is given by mass and speed
in the fact that power measures the exchange of energy per unit of time.
just a matter of terminology; otherwise, they are not different.
the units: power is measured in horsepower and energy in watts.
17
A 1000-kilogram car accelerates by 0.4 meters per second squared. According to Newton’s second law, we would say
the net force on the car is 400 newtons.
the net force on the car is 2500 newtons.
the reaction force is 1000 kilograms.
the kinetic energy of the car is constant.
18
In order to run, a woman learns to push on the ground supporting her. According to Newton’s third law , the reaction is
the force exerted on her joints by her muscles.
the force of gravity pulling on her.
mental anguish.
the force exerted on her by the ground.
19
A kilowatt-minute, though not a commercially used unit, would be a unit of
force
power
energy
acceleration
20
Water is pulled from the top of a dam to the bottom by the gravitational force. We would say
work is not involved in this situation
the work due to gravity is zero because the water is unaccelerated.
the work due gravit is positive, work and force are in the same direction
the work due to gravity is negative because gravity pulls down the water
