Unit 4: Physics
In a physics experiment, a 2.6-gram projectile travels at a velocity of 8.7 meters per second. What is the kinetic energy of the projectile as it flies through the air?
0.098397 kg ∙ m/s2
A machine accomplished 583 joules of work in 1.56 hours. How much power was required to do this?
0.1 watts
A circle has _____ center(s) of focus
1
What Mechanical Advantage would an inclined plane with a length of 8.5 meters reaching a height of 0.5 meters have?
17
It requires 25 N of force to move a 90 kg box 120 meters across a warehouse floor, then lift it 0.5 meter to put it in a truck. Calculate the total work done to load this box.
3,441 J
A rope is tied to a bucket in a well. The other end is tied a cylinder at the top to wind the rope and pull up the bucket. The cylinder has a crank handle attached that is 30 cm long. The radius of the cylinder is 10 cm. How much force must be applied to the crank handle to provide enough torque to lift a 20 kg bucket of water
65.3 N
You are an engineer who is in charge of production in a factory. A new machine purchased for the manufacturing line has an efficiency of 60%. The total work input was 1,162 newtons. What was the machine's useful work output?
697.2 N
Two objects with a positive charges have a repulsive force between them. To reduce that force to 1/49 of its original strength, you would need to move the two objects a distance of _____ times the original distance from their centers.
7
What is the potential energy of a meteor with a mass of 8.5 kg that is 89 km above the earth's surface?
7,413,700 kg ∙ m2/s2
Kepler's third law is:
T2=a3 the law of periods
The scientist who wrote the law of universal gravitation was _____
Isaac Newton
The formula for the potential energy of the water behind the dam is _____
PE = mgh
In a closed system, the formula for the conservation of energy is _____
PEi+KEi=PEf+KEf
What is Kepler's first law?
Planetary orbits are elliptical, not circular. The sun (not the earth!) forms one of the foci of the ellipse.
What is the formula for Coulomb's Law?
F=kcq1q2d2
_____ was the scientist who computed the value of G,G, the constant representing the force of gravitation.
Henry Cavendish
What is Kepler's second law?
The line joining the planet to the sun sweeps out equal areas in equal times as the planet travels around the ellipse.
law of moments
a law that states that a force times a distance on one side of a fulcrum is equal to a force times a distance on the other side of a fulcrum
law of conservation of energy
a law that states that the internal energy of a closed system remains constant
lever
a machine that enables a person to redirect or dilute the force necessary to accomplish work by spreading it over a longer distance
Mechanical Advantage
a measurement of the amplification of a force gained through a machine
Define rotational equilibrium:
a point at which an object has no torque acting upon it that would overcome rotational inertia the object's rate of turning or rotational acceleration does not change
rotational equilibrium
a point at which an object has no torque acting upon it that would overcome rotational inertia; the object's rate of turning or rotational acceleration does not change
Define translational equilibrium:
a point at which an object is experiencing no change in acceleration no forces are changing the object's translational motion
translational equilibrium
a point at which an object is experiencing no change in acceleration and, therefore, no forces are changing the object's translational motion
Center of focus is _____.
a point within a rounded object that is exactly the same distance from every point on the object's circumference
circle
a rounded object with one center of focus
ellipse
a rounded object with two points of focus
Define gravitation
a universal force that pulls every object in the universe, no matter how large or small, toward every other object in the universe
If you push a standing garden cart and it moves, you have changed its speed from 0 m/s to 2 m/s. This was giving the cart _____ because you changed its velocity.
acceleration
circumference
an outer boundary
Two objects with unlike electrical charges, such as positive and negative _____ each other
attract
Gravitational force is only _____
attractive
weak nuclear force
a fundamental force in the atom that is electromagnetic and responsible for nuclear decay
strong nuclear force
a fundamental force that binds positively charged protons and neutrally charged neutrons in an atom's nucleus together
Define strong nuclear force
a fundamental force that binds protons and neutrons in an atom's nucleus together
Define weak nuclear force
a fundamental force that is a short-range force inside an atom, responsible for nuclear decay
The fact that potential energy may be converted to kinetic energy and vice versa and energy will never disappear is due to the law of _____ of energy.
conservation
Simple Machines that afford Mechanical Advantage through a system of ropes and pulleys are _____.
pulley systems
To find the Mechanical Advantage of a wheel and axle you divide the _____ of the larger wheel by the radius of the _____ wheel.
radius smaller
An object with positive charge will _____ an object with positive charge
repel
Two objects with like electrical charges, such as positive and positive or negative and a negative, will _____ each other.
repel
The formula ∑τ=0 is associated with _____ equilibrium.
rotational
repulsive
tending to drive away or keep at a distance
coulomb
the SI unit that is equal to the quantity of charge that is transferred in one second across a conductor in which a current of one ampere exists
efficiency
the actual amount of Mechanical Advantage realized from the use of a machine; it is equal to the useful work output divided by the total work input
Define work
the amount of energy needed to move an object
work
the amount of energy required to move an object
Define power
the amount of work done in a given time
power
the amount of work done in a given time
fulcrum
the axis on which a bar can pivot; also called the point of rotation
In what ways does a screw gain Mechanical Advantage?
the screw is an inclined plane wrapped around a core leverage of the lever arm used to turn the screw by use of a wheel and axle
A balance point is:
the sum of all the torques equals 0. the forces on one side of the fulcrum equal the forces on the other side of the fulcrum the forces on both sides cancel each other
When a planet moves farther from the sun its speed _____
decreases
How does an inclined plane gain Mechanical Advantage
determined by the distance the load is moved divided by the final height to which it is lifted
The components of work are:
displacement force
An archer pulls back the string on his bow after connecting an arrow to the string. In the formula PEelastic=1/2kx2, the xx represents _____
distance the bow string is pulled
You apply a 200-N force to a box from the left, while another person simultaneously pushes on the same box from the right with an equal amount of force. No work is done because the _____ is zero.
distance the object moved
1. 1 g • cm/s2
dyne
Laws created according to observation and experimentation are _____.
empirical
A definition of _____ is the ability to do work
energy
By placing machines that are combinations of levers, pulleys and pivoting axles into _____, large amounts of work may be done with small amounts of force
equilibrium
If you were to calculate the amount of work an ant could perform carrying a load 30 cm, you would probably measure it in _____.
ergs
2. 550 ft-lb/s
horsepower
amount of work a draft horse can accomplish in one second
horsepower
perihelion
in a planet's orbit, its closest position to the sun
aphelion
in a planet's orbit, its farthest position from the sun
knife blades scissors pliers
inclined planes inclined planes, levers inclined planes, levers
ramps screws chisels
inclined planes inclined planes, wheel and axle inclined planes
Coulomb's law states that the electrical force between two objects will decrease when the distance between the two objects _____.
increase
When a planet moves closer to the sun its speed ____
increases
A type 3 lever _____ the distance the load moves which requires more _____.
increases effort
3. 1 N • m
joule
SI unit used to express work
joule or dyne
The amount of work necessary to move an object can be expressed in _____.
joules
Work is measured in _____.
joules
In the work-energy theorem, work is the change in _____ energy
kinetic
On September 24, 2011, 26 pieces of a satellite were predicted to fall to the earth's surface. Once the satellite pieces began to fall, their potential energies were converted to _____, or energy that objects possess due to motion.
kinetic
Law that states that every object in the universe attracts every object in the universe:
law of universal gravitation
empirical laws
laws created according to observation and experimentation
A lever's Mechanical Advantage can be calculated by _____.
length of effort arm/length of resistance arm
A(n) _____ is a machine that enables a person to redirect or reduce the force necessary to accomplish work by spreading it over a longer distance
lever
A(n) _____ is a device that transmits or modifies the force or the motion necessary to accomplish work.
machine
Two large planets may have high gravitational pull between them because the strength of gravity is partially based upon:
mass
On September 24, 2011, 26 pieces of a satellite were predicted to fall to the earth's surface. Once the satellite pieces began to fall, their potential energies were converted to kinetic energy. These pieces hit the earth with the force of their _____ energy or their potential energy combined with their kinetic energy.
mechanical
You use a lever to lift a heavy box off of a pallet. To lessen the amount of force you needed to lift the box you received _____.
mechanical advantage
How much work is performed pulling a 1200 kg car 100 meters down the road in 40 seconds?
not enough information
The measurement of the Force (F)(F) times the distance rr (the length in meters of the lever arm) that causes rotational motion is the definition or _____.
torque
If you push a standing garden cart and it moves, you have changed its speed and direction or _____.
velocity
4. 1 J/s
watt
used to express power
watt
A(n) _____ or _____ may be used to express power
watt horsepower
A joule is equivalent to a _____.
watt-second
Gravitational force is the _____ of the four fundamental forces
weakest
A simple machine in which you gain Mechanical Advantage due to the attachment of a larger wheel to a smaller wheel is a(n) _____.
wheel and axle system
Define electromagnetism
when electrical charges move, an electrical field magnetism is created a fundamental force that is responsible for electrically charged particles interacting with each other
A little girl at a daycare pushes a toy wooden duck. She applied force to move the mass a distance: therefore she performed _____
work
Wnet
work
You are changing a flat tire. The lug nuts that hold the tire to the rim require 135 N-m to loosen. Your lug wrench is 0.3 m long. Your mass is 50 kg. If you could apply all of your weight to the end of the lug wrench, could you loosen the nuts?
yes, just barely
The formula for torque is _____
τ=F⋅r
Another name for the fulcrum is _____
point of rotation
center of focus
point within a rounded object that is exactly the same distance from every point on the object's circumference
The electrical charge on an object -either positive or negative- constitutes the object's _____
polarity
polarity
positive or negative electrical charge
On September 24, 2011, 26 pieces of a satellite were predicted to fall to the earth's surface. Since the satellite pieces were orbiting the earth from a height of 50 miles, they had _____, or energy due to their position.
potential
A small car engine has a capacity of 74 horsepower. The 74 horsepower refers to the car's average _____ capability.
power
If we measured the rate work is accomplished, we would be measuring _____.
power
To do a certain amount of work in less time requires more _____
power
How much work would a crane do to lift a 1200 kg car 10 meters?
117,600 J
How much force must be applied to the end of a 0.1 m long wrench to torque a bolt to to 12 N-m?
120 N
The scientist who found that charges on objects were proportional according to Felectric=kcq1q2d2 was _____.
Charles-Augustin de Coulomb
Before Kepler wrote his three laws, people believed that earth and the planets in the solar system revolved around the _____.
Earth
What is Kepler's third law?
For any planet, the square of the period of revolution about the sun is proportional to the cube of the average distance from the sun.
The gravitational constant
G=6.67×10−11 N⋅m2/kg2
The scientist who just discovered that the earth and other planets rotate in elliptical orbits around the sun, that the square of the period of revolution about the sun is proportional to the cube of the average distance from the sun and that the line joining the planet to the sun sweeps out equal areas in equal times as the planet travels around the ellipse was _____.
Johannes Kepler
The formula for the kinetic energy of the water flowing from the dam is _____
KE = 1/2mv2
Only friction between the air and the satellite piece prevents the formula from the conservation of energy from being completely accurate. This is stated as _____.
KEi+PEi=KEf +PEf
The formula F1d1=F2d2 states that the force times the distance on one side of a lever's fulcrum equals the force times the distance on the other side of the fulcrum, this is the _____.
Law of Moments
machine
a device that transmits or modifies the force or the motion necessary to accomplish work
A planet's farthest position to the sun is _____
called the aphelion
A planet's closest position to the sun is _____
called the perihelion
Objects fall toward the _____ of the earth due to their attraction by gravity.
center
When computing the gravity acting upon an object, one needs to assume gravity is focused upon the object's _____.
center of mass
The _____ of a machine or actual Mechanical Advantage is measured by dividing the useful work output by the total work input.
efficiency
If you push a standing garden cart and it moves, you have applied a(n) _____ to a(n) _____.
force mass ?
The reason that a machine does not have a 100% efficiency is due to _____.
friction
A(n) _____ is the axis on which a bar can pivot; also called the point of rotation
fulcrum
The trajectory of cannons may be adjusted to reach different targets since the cannon's weight is balanced on a _____.
fulcrum pivot point
In addition to a screw being an inclined plane, it also gains M.A. through a wheel and axle, with the wheel being the ______ of the tool used to turn the screw and the smaller circle of the axle being the screw's _____.
handle core
Gravity is subject to the strength declining in inverse proportion to the square of the distances from the centers of two objects.
inverse-square law
An archer pulls back the string on his bow after connecting an arrow to the string. In the formula PEelastic=1/2kx2 , the constant k is determined by the string's _____ while PEelastic represents _____.
size and material spring ?
Brahe thought the earth was the center of the solar system.
true
The use of simple machines can make work easier by requiring less effort to gain the same results.
true
The use of three pulleys gives you more Mechanical Advantage that the use of one.
true
