Answer:
8 units
Explanation:
- Thermal Energy Test
The front door of a home is made of steel. When it is warm outside, the door sticks and is difficult to open or close. When the weather is cool, the door
does not stick. Which statement best explains the difference in the behavior of the door when the weather is warm compared to when it is cool?
A. When a material contracts, it increases in volume due to an increase in kinetic energy.
a
B. Different materials expand and contract at the same rates due to the kinetic energy being the same.
C. Thermal expansion makes the door fit better when it is cooler due to a decrease in kinetic energy.
D. The metal in the door expands when it becomes warm due to an increase in kinetic energy, and contracts when it's cooler.
Answer:D. The metal in the door expands when it becomes warm due to an increase in kinetic energy, and contracts when it's cooler.
Explanation:
because the metal in the door expands due to warm to an increase in kinetic energy and contracts.
A fan has four identical, symmetrically placed blades. The blades are rotating clockwise at twenty revolutions per second.
A) What is the smallest time interval between stroboscope flashes that will make the fan blades appear motionless?
B) What is the highest frequency (in flashes per second) at which a stroboscope will make the
fan blades appear to stand still? Show your calculation.
C) The same questions as (a) and (b), but someone has put a yellow dot on one blade, and now you want the yellow dot to appear to be standing still. Explain, and show your calculation.
D) Now the stroboscope is set for nineteen flashes per second, and the yellow dot appears to be slowly rotating. Which direction does it appear to rotate, clockwise or counterclockwise? Explain, and show your calculation.
E) The same as (d), but the stroboscope is set for twenty-one flashes per second. Explain, and show your calculation.
Answer:
A) t = 1.249 10⁻² s, B) f = 80 Hz, C) f = 20 Hz,
D) slowly advancing an angle of approximately Δθ = 0.05 rad each flash
E) In each flash it seems to go backward an angle of Δθ = -0.05 rad
Explanation:
A) To make it appear that the blades are immobile, it implies that every time the light turns on, a blade should be in the same position, therefore, as we have 4 blades, they must rotate an angle of 2π/4,
θ = π / 2
θ = 1.57 rad
taking the angle let's use the endowment kinematics relations
θ = w₀ t + ½ α t²
in general the fans rotate at constant speed α= 0
θ = w₀ t
t = θ / w₀
let's reduce the magnitudes to the SI system
w₀ = 20 rev / s (2π rad / 1rev) = 125.66 rad / s
let's calculate
t = 1.57 / 125.66
t = 1.249 10⁻² s
B) the fastest speed for the blades to rotate is when one blade of a complete turn , we use the relationship between the fecuance and the period
f = 1 / T
f = 1 / 1.25 10⁻²
f = 80 Hz
C) we have two possibilities:
* a yellow dot is placed on each sheet
In this case the angular velocity of the blade is the same at all points, therefore the results obtained should not change
* a yellow dot is placed on a single sheet.
Here for the point to remain fixed the angle of rotation must be
θ= 2π rad
the time is
t = 2π / 125.66
t = 5 10⁻² s
the maximum frequency is
f = 1/5 10⁻²
f = 20 Hz
D) The copy strobe rotates at f = 19 Hz, the time between each flash is
t = 1/19
t = 5.26 10⁻² s
this time is higher, so the angle turned is large
θ = w t
θ = 125.66 5.26 10⁻²
θ = 6.61 rad
the relationship between this angle and the angle of a circle is
θ = 1,052
We can see that it is this time the blade rotates 1 complete turns, for this the position of the blade changes us, for the other 0.052 rad the blade rotates a little more than the circumference therefore it seems that it is slowly advancing an angle of approximately
Δθ = 0.05 rad each flash
E) in this case changes the flash speed
t = 1/21
t = 4.76 10⁻² s
the angle rotated is
θ = 125.66 4.76 10⁻²
θ = 5.984 rad
θ / 2π = 0.95
in that case, the blade did not complete the turn, therefore in each flash it seems to go backward an angle
Δθ = -0.05 rad
Work is done on an object when
A) The displacement is not zero
B) The force and the displacement are perpendicular
C) The displacement is zero
D) The force is zero
Answer:
Incomplete question but the closest ans is
A) The displacement is not zero
Explanation:
For work to be done, the direction of force has to be parallel to or in the same direction as the displacement, this can then be calculated by
[tex]W=Fs \ cos[/tex]θ
Where θ is the angle between direction of force and direction of displacement
By this equation,
if Force is zero, W is zero
if displacement is zero, W is zero
if force and displacement are perpendicular θ=90, cosθ = 0
So A is the cloest choices
A 2.0-kg mass is projected from the edge of the top of a 20-m tall building with a velocity of 24 m/s at some unknown angle above the horizontal. Disregard air resistance and assume the ground is level. What is the kinetic energy of the mass just before it strikes the ground?
Answer:
968 J
Explanation:
The computation of the kinetic energy is shown below:
Given that
mass m = 2 kg
height h = 20 m
velocity v = 24 m / s
Now
According to the law of conservation of energy ,
= K.E at top + P.E at top
= ( 1 ÷ 2) mv ^ 2 + mgh
= 576 + 392
= 968 J
The kinetic energy of the mass just before it strikes the ground is 968 J.
The given parameters:
Mass of the object, m = 2.0 kgHeight of the building, h = 20 mInitial velocity of the mass, u = 24 m/sThe kinetic energy of the mass just before it strikes the ground is calculated by applying the principle of conservation of energy;
[tex]K.E_f = K.E_ i + P.E_i\\\\K.E _f = \frac{1}{2} mv^2 + mgh\\\\K.E_f = \frac{1}{2} \times 2\times 24^2 \ + \ 2 \times 9.8 \times 20\\\\K.E_f = 968 \ J[/tex]
Thus, the kinetic energy of the mass just before it strikes the ground is 968 J.
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List down the types of centripetal force?
Answer: Just a few examples are the tension in the rope on a tether ball, the force of Earth's gravity on the Moon, friction between roller skates and a rink floor, a banked roadway's force on a car, and forces on the tube of a spinning centrifuge. Any net force causing uniform circular motion is called a centripetal force.
Answer:
roller skates and a rink floor, a banked roadway's force on a car, and forces on the tube of a spinning centrifuge
Explanation:
The tray dispenser in your cafeteria has broken and is not repairable. The custodian knows that you are good at design-ing things and asks you to help him build a new dispenser out of spare parts he has on his workbench. The tray dispenser supports a stack of trays on a shelf that is supported by four springs, one at each corner of the shelf. Each tray is rectangu-lar, with dimensions 45.3 cm by 35.6 cm. Each tray is 0.450 cm thick and has a mass of 580 g. The custodian asks you to design a new four-spring dispenser such that when a tray is removed, the dispenser pushes up the remaining stack so that the top tray is at the same position as the just-removed tray was. He has a wide variety of springs that he can use to build the dispenser. Which springs should he use
Answer:
you have to find 4 spring with this elastic constant k = 316 N / m
Explanation:
In this case for the design of the dispenser the four springs are placed in the four corner at the bottom, therefore we can use the translational equilibrium relationship
4 F_e -W = 0
where the elastic force is
F_e = k x
we substitute
4 kx = mg
k = [tex]\frac{mg}{4x}[/tex]
Each tray has a thickness of x = 0.450 cm = 0.450 10⁻² m, this should be the elongation of the spring so that when the tray is in position it will remain fixed.
let's calculate
k = [tex]\frac{0.580 \ 9.8}{4 \ 0.450 \ 10^{-2} }[/tex]
k = 3.1578 10² N / m
k = 316 N / m
therefore you have to find 4 spring with this elastic constant
The Willis Tower in Chicago has an observation deck 412 m above ground.
How far can you see out over Lake Michigan from the observation deck?
Answer:
Check Newton's Rings:
d = height of air film
s = distance from center to ring being considered
R = radius of circle considered
The approximate formula is:
d = s^2 / (2 R) or s = (2 R d)^1/2
If we just use 4000 mi for R and 1/4 mi for d the height
we get s = (2 * 4000 * 1/4)^1/2 = 2000^1/2 mi = 45 mi
What is the largest source of
thermal energy in our Solar System? Does this energy
reach us through conduction, convection, or radiation?
please help me
Answer:
sun itself is the main source of thermal energy.radiation
A point charge gives rise to an electric field with magnitude 1 N/C at a distance of 3 m. If the distance is increased to 6 m, then what will be the new magnitude of the electric field?
Answer:
The magnitude of the final electric field is 0.5 N/C.
Explanation:
Given;
initial electric field, E₁ = 1 N/C
initial distance moved by the charge, r₁ = 3 m
final distance moved by the charge, r₂ = 6 m
let the magnitude of the final electric field = E₂
The electric potential created by the charge is given as;
V = E₁r₁ = E₂r₂
[tex]E_2 = \frac{E_1r_1}{r_2} \\\\E_2 = \frac{1 N/C\ \times \ 3m}{6m} \\\\E_2 = 0.5 \ N/C[/tex]
Therefore, the magnitude of the final electric field is 0.5 N/C.
A high-voltage transmission line carries 1,000A at 700,000 V. What is the power carried by the line?
If the resistance in the wire is 1ohm/mile and the line is 110 miles long, what is the power loss due to resistive losses in this wire?
a. 11kW
b. 110kW
c. 11 MW
d. 110 MW
Answer:
d. 110 MW
Explanation:
The computation of the power loss is given below:
= I^2 × R
= 1000^2 × 110
= 110 × 10^6 W
= 110 MW
Here I represent the current through the resistance
ANd, R represent the resistance
So, the correct option is d
what is a resultant vector
Answer:
A resultant vector is a combination or, in simpler words, can be defined as the sum of two or more vectors which has its own magnitude and direction.
1.A boy runs at a speed of 3.3 m/s straight off the end of a diving board that is 3 meters above the water
2.What is the horizontal distance the boy in # 1 travels while in the air ?
If a boy runs at a speed of 3.3 m/s straight off the end of a diving board that is 3 meters above the water, then the horizontal distance traveled by the boy would be 2.58 meters.
What are the three equations of motion?There are three equations of motion given by Newton,
v = u + at
S = ut + 1/2 × a × t²
v² - u² = 2 × a × s
As given in the problem if a boy runs at a speed of 3.3 m/s straight off the end of a diving board that is 3 meters above the water,
3 = ut + 1/2 × a × t²
3 = 0 + 0.5 × 9.8 × t²
t = 3 / 4.9
t = 0.7824
The horizontal distance traveled by the boy = 3.3 × 0.7824
= 2.58 meters
Thus, the horizontal distance traveled by the boy would be 2.58 meters.
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This is a problem about a child pushing a stack of two blocks along a horizontal floor. The masses of the blocks, and the coefficients of friction between the two blocks and between the lower block and the floor will be given. In order to do the pushing, the child will only be touching one of the two blocks. The mass of the upper block in the stack is 0.760 kg . The mass of the lower block in the stack is 1.630 kg . The coefficients of friction between the two blocks are: static 0.790, and kinetic 0.660. The child's mother, who likes to encourage his experiments, has oiled a small strip of the horizontal floor so that it is very slick; the coefficient of kinetic friction between the oiled section of floor and the lower block is only 0.080 and the coefficient of static friction is insignificantly different. Before the pushing starts, here is a question about the vertical forces acting on the two blocks.
Required:
What is the vertical component of the contact force on the lower block by the floor?
Answer:
N = 23.4 N
Explanation:
After reading that long sentence, let's solve the question
The contact force is the so-called normal in this case we can find it by writing the translational equilibrium equation for the y axis
N - w₁ -w₂ =
N = m₁ g + m₂ g
N = g (m₁ + m₂)
let's calculate
N = 9.8 (0.760 + 1.630)
N = 23.4 N
This is the force of the support of the two blocks on the surface.
what is the formula of magnetic force
Answer:
F = qvB sinθ
(Hope this helps! Btw, I am the first to answer. Brainliest pls! :D)
A bar magnet is attached solidly to a frictionless surface and its length is aligned with the x axis.To the right of the first magnet a short distance away is a second bar magnet with its center placed on the x axis and its length perpendicular to the x axis.The second magnet is free to move.Once placed in position at rest,which best describes the initial motion of the second magnet?
a. The magnet will move away from the fixed magnet.
b. The magnet will not move.
c. The magnet will move toward the fixed magnet.
d. The magnet will start to rotate.
Answer:
the correct answer is D
Explanation:
For this exercise we must remember that the poles of the same if not repel each other and the poles of different signs attract.
With this, let's analyze the situation presented.
The two magnets are perpendicular, with the second magnet to the right of the first.
We have two cases:
* first magnet with the north pole to the right
If the north of the second magnet is upwards there is a repulsion and the south pole of the second magnet there is an attraction with the north pole of the first magnet, so it would have a force that has to rotate the second magnet.
The force with the south pole of the first magnet that is at a greater distance is less, so the resultant of force is determined by the nearest poles.
If the poles of the second magnet are reversed, that is, the South pole up and the North pole down, the same result is obtained, but with a twist in the opposite direction.
* first magnet with the south pole to the right
Repels with the south pole of the second magnet and attracts with the north of the second magnet
therefore in both possibilities the second magnet acquires a rotational movement
Consequently the correct answer is D
Calculate the amount of heat given off by 640 g of water cooling from 76 °C to 28° C. Specific heat of water = 4.816 J/g C. Show your step by step process on how you have arrived at your answer. *
Answer:
47947.52 J.
Explanation:
From the question,
Amount of heat given of (Q) = mc(t₁–t₂).................... Equation 1
Where m = mass of water, c = specific heat capacity of water, t₁ = initial temperature, t₂ = final temperature.
Given, m = 640 g = 640 g, c = 4.816 J/g°C, t₁ = 76 °C, t₂ = 28 °c.
Substitute these values into equation 1 above
Q = 640×4.816(48)
Q = 147947.52 J.
Hence the amount of heat given off is 47947.52 J.
A 5.0-kg object is suspended by a string from the ceiling of an elevator that is accelerating downward at a rate of 2.6 m/s2. What is the tension in the string (in N)?
Answer:
36N
Explanation:
First draw a diagram so you can see which forces act in which direction.
Then define which is your positive direction. I chose the direction of accelleration (downward) to be positive. This means that the weight of the object is also acting in the positive direction but Tension is acting in the negative direction.
If the elevator which contains the object within is accellerating at 2.6 ms^-2 then the object and string system is also accellerating at the same rate.
F = ma where F is the resultant force.
Resultant for is Weight + Tension but tension is in the negative direction so
F = mg -T
F = 5g - T
F = ma so F = 5 x 2.6
13 = 5g-T
T = 5g - 13
T = 36N
(I've taken g = 9.8ms^-2 but if this is for a physics class I'd take it to be 9.81ms^-2)
We have that For a 5.0-kg object is suspended by a string from the ceiling of an elevator that is accelerating downward at a rate of 2.6 m/s2 he tension in the string (in N) is
T=62N
From the question we are told
A 5.0-kg object is suspended by a string from the ceiling of an elevator that is accelerating downward at a rate of 2.6 m/s2. What is the tension in the string (in N)
Generally the equation for the Tension is mathematically given as[tex]T=mg+ma\\\\T=5*(9.8+2.6)\\\\T=62N[/tex]
Therefore
For a 5.0-kg object is suspended by a string from the ceiling of an elevator that is accelerating downward at a rate of 2.6 m/s2 he tension in the string (in N) is
T=62N
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Metals are amazing, and they are all around us. You can probably easily identify them by their shiny surfaces and tinny sound when you tap them.
a. True
b. False
Answer:
a. True
Explanation:
Metals are amazing, and they are all around us. You can probably easily identify them by their shiny surfaces and tinny sound when you tap them.
Generally, metals are mainly hard, shiny, and can be hammered into thin sheets. Also, another property of a metal is that, it is a good conductor of heat and even electricity because there valence (outer) electrons are delocalized. Some examples of chemical elements that are metals are iron, gold, sodium, silver, copper etc.
Hot water is poured into a mug and the mug gets hot. This is an example of which type of energy transfer?
A) radiation
B) conduction
C) convection
D) This s not an energy transfer
PLEASE HELP ME
The answer is B: Conduction
When driving across Death Valley in the summertime, it is recommended that you release some air from your tires before making the crossing. Using the principles of Kinetic Molecular Theory (KMT), explain why it is a good idea to follow this recommendation.
According to the ideal gas law, pressure will rise as a gas's temperature rises. There is a limit to how much the tire can expand before the rubber gives in to the pressure build-up.
What the principles of Kinetic Molecular Theory?For every 10 degrees that the temperature drops, the inflation pressure in tires typically decreases by 1 to 2 psi. Moreover, as the tire pressure heats up during the first 15 to 20 minutes of driving, it will increase by one psi every five minutes.
The ideal gas law states that pressure will increase as a gas's temperature increases. Before the rubber gives in to the pressure build up, the tire can only expand so far.
Therefore, The pressure in your tires will increase due to the increased particle movement in hot air, which will cause the centre of the tread to bow out and wear out first. Increasing the demand for new tires.
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1. A ball with a mass of 2.3 kg travels with a velocity of 10 m/s. What is it's kinetic energy?
Answer:
KE=½mv²
KE=½2.3kg×(10m/s)²
KE=½2.3kg×100m²/s²
KE=2.3kg×50m²/s²
KE=115joules
A student is conducting an experiment to compare the resistivity of two unknown materials by using two wires, each made of one of the materials and each connected in a circuit. The student measures the potential difference across and current in the wires. What must be the same to be able to compare the resistivities using just the potential difference and current measurements?
Answer:
is there a. b. c or d?
Explanation:
The lever shown above can be used to move the
bowling ball off the shelf. Pushing down at what
point on the lever would require you to apply the
least amount of force to move the ball?
A. 1
B. 2
C. 3
D. 4
Answer:
C your answer would be C
Explanation:
It should be right
Explain how a common housecat gets “worms.”explain(science)
Answer:
Ingenstion
Explanation:
The most common tapeworms that infect cats worldwide are Dipylidium caninum and Taenia taeniaeformis. Dipylidium caninum is transmitted to cats by fleas. The immature fleas larvae ingest the eggs of the worm, but infection is then passed on to a cat when it swallows an infected flea during grooming.
Answer:
The most common worms that housecats get are tapeworms. The housecats always lick their fur to clean them. The tapeworms love where it is damp. After the housecats clean their fur, they will play in the house sometimes they will roll on the floor. Then they get tapeworm eggs, after the eggs hatch the tapeworm will live on the fur of the cats.
Explanation:
[GT.01]The diagram below shows a portion of the geologic time scale.
Based on the time scale, it can be concluded that
flowering plants appeared on Earth before animals.
animals appeared on Earth before flowering plants.
flowering plants created the first oxygen molecules.
land animals created the first oxygen molecules.
Answer:diagram....???
geologic time scale what evolve
Answer:
If below is the same diagram:
B. animals appeared on Earth before flowering plants.
good luck, i hope this helps :)
Are Saturated fats healthy?
Answer:
Its not as harmful as trans fat, saturated fat can raise bad LDL cholesterol and too much can negatively impact heart health, so it's best consumed in moderation. While there's no need to cut out all saturated fat from your diet, most nutrition experts recommend limiting it to about 10% of your daily calories.
Explanation:
(LDL stands for low-density lipoproteins. It is sometimes called the "bad" cholesterol because a high LDL level leads to a buildup of cholesterol in your arteries.)
A spring with a constant of 76 N/m is extended by 0.9 m. How much energy is stored in the extended spring?
Answer:
[tex]E=30.78\ J[/tex]
Explanation:
The force constant of the spring, k = 76 N/m
The extension in the spring, x = 0.9 m
We need to find the energy is stored in the extended spring. The energy stored in the spring is given by :
[tex]E=\dfrac{1}{2}kx^2\\\\E=\dfrac{1}{2}\times 76\times (0.9)^2\\\\E=30.78\ J[/tex]
So, 30.78 J of energy is stored in the spring.
PLEASE HELP IS URGENT
A current of 2A flows through a resistor for 30s.
(a) How many Coulombs of charge pass through in that time?
(b) Ifa total of 300J of energy are produced in that time, how many joules will be
produced when just 1C of charge passes?
(c) By referring to the definition of a volt, how great will be the p.d. in volts across the
resistor?
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A garbage truck and a minivan are moving at the same velocity.
Which automobile will have greater momentum and why? Explain your response using Newton’s second law of motion specifically.
If the garbage truck and minivan in Part A get into an accident with each other, how can safety restraints in a car can save a life? Explain your response using one of Newton’s laws.
Which of Newton’s laws of motion act upon the vehicles at the point of impact? Explain your answer.
Answer:
Part A
Newton's second law of motion states that the force applied to an object is directly proportional to the rate of change of momentum that is produced
Mathematically, we have;
F = m·v - m·u/Δt
Where;
m = The mass of the object
v = The final velocity of the object
u = The initial velocity of the object
Δt = The duration of motion of the object during change in velocity
Therefore, given that the mass, 'M', of the truck is larger than the mass, 'm', of the minivan, where the time of change in velocity Δt, and the initial and final velocities of both automobiles are the same such as in a sudden stop, the garbage ruck will exert more force than the minivan, and therefore, the garbage truck has a greater initial momentum before the automobiles are brought to a stop
Part B;
According to Newton's first law of motion, we have;
The use of a seat belt (and airbag for front seated passengers) will prevent dashboard or windscreen for the front passengers or the front seat for the passengers in the back, from being the item that stops the continued forward motion of the passengers in the car, which can lead to injury
Part C; The Newton's law of motion that act on a body at the point of impact is Newton's third law of motion, which states that the action and reaction are equal and opposite
Therefore, the action of the garbage truck on the minivan upon impact is equal to the reaction of the minivan to the force the garbage truck exerts on the minivan
Explanation:
You are conducting an experiment inside an elevator that can move in a vertical shaft. A load is hung vertically from the ceiling on a string, and is stationary with respect to you. The tension in the string is measured to be exactly equal to the force due to gravity on the load. No other forces are acting on the load. Which of the following statements about the elevator are correct?
A. The elevator is an inertial frame of reference.
B. The elevator is not an inertial frame of reference.
C. The elevator may be at rest for the duration of the entire experiment.
D. The elevator may be moving at a constant velocity upward.
E. The elevator may be moving at a constant velocity downward.
F. The elevator must be accelerating
Answer: B. The elevator is not an inertial frame of reference.
F. The elevator must be accelerating.
Explanation:
Since we've been given the information that the tension in the string is measured to be exactly equal to the force due to gravity on the load and that no other forces are acting on the load, the statements about the elevator that are correct include:
• The elevator is not an inertial frame of reference.
• The elevator must be accelerating.
If the elevator isn't accelerating, the tension in the string can't be equal to the force of gravity.
