Because when we polish the shoes, they gain charges or the shoes become charged, the small non-charged particles are attracted to them.
Need help with this question. Thirty points.
[tex]1)\\\\\text{Kinetic energy,}\\\\E_k = \dfrac 12 mv^2 \\\\\implies m = \dfrac{2E_k}{v^2} = \dfrac{2\times 4500}{30^2}=10~ kg\\ \\2)\\\\\text{Kinetic energy,}\\\\E_k = \dfrac 12mv^2 \\\\\implies v^2 = \dfrac{2E_k}m\\\\\implies v = \sqrt{\dfrac{2E_k}{m}}=\sqrt{\dfrac{2 \times 320}{\dfrac{20}{9.8}}}= 17.709 ~ ms^{-1}\\\\3)\\\\\text{Kinetic energy,}\\\\E_k=\dfrac 12 mv^2=\dfrac 12 \times 50 \times 10^2=2500 ~J\\\\\\[/tex]
[tex]4)\\\\\text{Potential energy,}\\\\E_p =mgh = 5\times 9.8\times 1.5 = 73.5 ~J[/tex]
Topic : Heat
1. Why can anyone put their fingers beside the flame of a lit candle without getting burned, but not above the flame?
2. What is the purpose of putting holes near the top of a metal lampshade?
3. A metal spoon is placed in one of two identical cups of hot coffee. Which cup will be cooler after a few minutes?
what property of light is suggested by the formation of shadows
Answer:
The reflection and rectilinear propagation of light helps in the formation of shadows and also tells light doesn't penetrate opaque materials.
An object absorbs red, orange, yellow, blue, indigo, and violet light. What color is it?
A. blue
B. green
C. indigo
D. red
Answer: B. Green
Explanation:
Since the object absorbs all the other options listed here, it will reflect green light. This makes the object appear green to our eyes.
Blue (A), indigo (C), and red (D) are listed in red, orange, yellow, blue, indigo, and violet. Green is not, so this is our answer.
Fun fact:
An example of this is grass!
Answer:
green
Explanation:
The SI unit for weight is ________.
A. mass
B. kilogram
C. newton
D. acceleration of gravity
E. weight
Answer:
Newton
Explanation:
The SI unit for weight is newton.
A satellite with a mass of 45 kg fires its rocket thrusters, which give an impulse of 1035 kg•m/s. What was the total change in the velocity of the satellite - that is, what was the total ΔV?
O 58 m/s
O 23 m/s
O 39 m/s
O 47 m/s
The total change in velocity of the satellite is 23 m/s
What is Impulse?In Physics, Impulse is the product of mass and change in velocity
Given:
mass = 46 kg
Impulse = 1035 kg•m/s
change in velocity = ?
impulse = mass * velocity
change in velocity = Impulse / mass
change in velocity = 1035 / 45
change in velocity = 23 m/s
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A solenoid has 450 loops each of radius 0.0254 m. The field increases from 0 T to 3.00 T in 1.55 s. What is the EMF generated in the coil? (Hint: What is the area of a circle) (Unit = Volts)
Answer:
0.175 second
Explanation:
i hope it helps
An elastic string of length 20cm stretch by 7mm under a load 50N . The strain in the spring is?
Answer:
0.035
Explanation:
7÷1000
=0.007m
0.007/0.2
=0.035
Mechanical strain of an elastic substance is the ratio of its change in length to the original length. The strain of the elastic string of length 20 cm when stretched by 7 mm is 0.035.
What is strain ?Strain is a physical quantity used to express the change in dimension of an elastic material. It is the ratio of change in length to the original length. Stress is the force that causing the deformation.
According to Hook's law of elasticity, the strain is directly proportional to the strain. They show a linear relation. Let L be the original length of a string and its change in length be ΔL.
Thus, strain = ΔL / L
Given that, the change in length = 7 mm = 0.7 cm
original length of the string = 20 cm
strain = 0.7 cm/ 20 cm
= 0.035
Therefore, the strain of the elastic string of length 20 cm when stretched by 7 mm is 0.035.
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Why do you think we need evidence to be able to continually test theories about the composition and origin of our solar system and galaxies?
We need evidence to be able to continually test theories about the composition and origin of our solar system and galaxies in order to verify the theories and to make laws.
What is theory?A theory is an explanation for observations of the natural world that has been carried by using the scientific method, and which brings together many facts.
So we can conclude that we need evidence to test theories about the composition and origin of our solar system in order to verify the theories and to make laws.
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a bulb rated 100 watt 120 volt is connected across a 120 volt source find the current in the bulb and power consumed by it
As it mentioned
100W/120VSo
power is 100W
Now
Current be I
[tex]\\ \rm\rightarrowtail I=\dfrac{P}{V}=\dfrac{100}{120}=\dfrac{5}{6}=0.8A[/tex]
The terminal velocity of a 3 × 10^-5 raindrop is about 9 m/s. Assuming a drag force Fd = −bv, determine (a) the value of the constant b and (b) the time required for such a drop, starting from rest, to reach 63% of terminal velocity.
Based on the data provided, the value of the constant b is 3.27 × 10^-5 kg/s and the time required to reach 63% of terminal velocity is 0.58 s.
What is terminal velocity?The terminal velocity of a body is the velocity at which the body falls at constant velocity through a fluid.
For the falling raindrop, let positive direction be downwards and negative direction upwards,
mass of the raindrop, m = 3×10-5 kg velocity at time t, is v(t)terminal velocity, v0 = 9 m/sgravitational acceleration, g = 9.81 m/s²The raindrop experiences a downward gravitational force mg, and an upward drag force -bv.
The total force at a time t is given as
F(t) = mg - bv(t)a)
Terminal velocity is achieved then the total force is 0,
0 = mg - bv0
Therefore
b = mg/v0
Substitutingthe values:
b = (3 × 10^-5 × 9.8)/9
b = 3.27 × 10^-5 kg/s
b) Applying Newton's Second Law
F = ma
where
a = v/tF = mgTherefore,
mg = mv/t t = v/g
however, t is at 63% velocity
thus:
t = 0.63v/g
t = 0.63 × 9 /9.8
t = 0.58 s
Therefore, the value of the constant b is 3.27 × 10^-5 kg/s and the time required to reach 63% of terminal velocity is 0.58 s
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Pls helppppp my last question!
Answer:
load
a generator, a light bulb (load) and a closed switch
Explanation:
as explained in the other question, the fan is using generated electric energy to create mechanical movement. as such it is a load on the grid or circuit or net.
and electric power can only flow, if there is a closed (uninterupted) circuit from the power source to a load and back.
any open switch is an interruption of the circuit.
a buzzer is a kind of switch. it closes the circuit (and puts a load on) only when somebody presses it.
by the way, a closed circuit without a load will "destroy" (short circuit) the power source or at least the wires (burn through).
A car accelerates to a speed of 55 m/s within the span of 8 seconds. If its acceleration
was 4 m/s2, what was its initial velocity? Show all work and units for full credit.
The initial velocity of a car that accelerates to a speed of 55 m/s within the span of 8 seconds is 23m/s.
How to calculate initial velocity?The initial velocity of a moving body can be calculated using the following formula:
a = v - u/t
Where;
a = acceleration (m/s²)v = final velocity (m/s)u = initial velocity (m/s?t = time (seconds)According to this question, a car accelerates to a speed of 55 m/s within the span of 8 seconds. If its acceleration was 4 m/s², the initial velocity is calculated as follows:
4 = 55 - u/8
32 = 55 - u
u = 55 - 32
u = 23m/s
Therefore, the initial velocity of a car that accelerates to a speed of 55 m/s within the span of 8 seconds is 23m/s.
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a hunter shoots a stone from his catapult with an initial velocity of 40 m per seconds add elevation of 60 degree with the aim of hitting a bird 145n away.
1. calculate the time of flight
Answer:
approximately 7 seconds
Explanation:
The given scenario is just an example of Projectile Motion.
In this question, we are given:
- Initial Velocity (u) = 40 m/s
- Angle of Elevation (θ) = 60 degrees
- Distance of Bird (s) = 145 meters [Not used for the time of flight]
Time of Flight:
[tex]T = \frac{2uSin(\theta)}{g}[/tex]
we will use g = 9.8 m/s/s since we are not told otherwise.
[tex]T = \frac{2(40)Sin(60 degrees)}{9.8}[/tex]
[tex]T = \frac{40\sqrt{3}}{9.8}[/tex]
T = 4.081(√3) seconds
rounded to 7 seconds
Which of the following is a renewable source of energy?
Tick one box.
A bio-fuel
B coal
C natural gas
D oil
Answer:
A. boi-gas
Explanation:
This may help u
A plant is sitting on a table.
What, if any, forces are acting on the plant? (If there are forces acting on the
plant, include what direction they are acting.)
1 - Gravity (down)
11- Static Friction
111 - Normal (support) Force (up)
IV - Air Resistance to the left)
V - Applied Force (to the right)
#1
Yes gravity is acting downwards
#2
No static friction as its at rest#3
Normal reaction is applied upwards#4
No air resistance$5
No Applied force
Two identical twins, Sallie and Serena, are playing one December on a large merry-go-round (a disk mounted parallel to the ground on a vertical axle through its center) in their school playground in northern Minnesota. Each twin has a mass of 30.9 kg. The icy coating on the merry-go-round surface makes it frictionless. The merry-go-round revolves at a constant rate as the twins ride on it. Sallie, sitting a distance 1.85 m from the center of the merry-go-round, must hold on to one of the metal posts attached to the merry-go-round with a horizontal force of 59.0 N to keep from sliding off. Serena is sitting at the edge, a distance of 3.64 m m from the center; Serena must also hold on to a metal post on the merry-go-round to keep from sliding off.
Required:
What is the ratio of Serena?s speed to Sallie's speed (both speeds are measured by a stationary observer watching the spinnning merry-go-round)?
For a twin mass of 30.9 kg, sitting at a distance of 1.85 m, with a horizontal force of 59.0 N the ratio of Serena's speed to Sallie's speed is mathematically given as
V= 2.06:1
Generally, the equation for the velocity is mathematically given as
v = w r
Therefore
[tex]\frac{v serena}{vsallie} = \frac{r serena}{r sallie}[/tex]
V= 3.63/1.76
V= 2.06
In conclusion, the ratio is
V= 2.06:1
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Plant and animal cells are both eukaryotic cells that share many organelles and cell structures in common. However, each have unique organelles that perform specific functions in each cell type. Examine each of the lists of cell structures. Which of these are found in plant cells? Select ALL that apply.
A) nucleus, ribosomes, and chloroplasts
B) mitochondria, cell wall, chloroplasts
C) nucleus, mitochondria, and centrioles
D) cell membrane, ribosomes, small vacuoles
E) cell wall, central vacuole, and cell membrane
Answer:
A) nucleus, ribosomes, and chloroplasts
B) mitochondria, cell wall, chloroplasts
D) cell membrane, ribosomes, small vacuoles
E) cell wall, central vacuole, and cell membrane
Explanation:
It cannot be C as the list features centrioles, which is an animal-cell only structure.
A person with a mass of 80 kg is at rest. What is their momentum? Write the
number only. *
Your answer
Answer:
0
Explanation:
because no distance covered by body
If interstellar gas has a density of 1 atom/cm3, how big a volume of material must be used to make a star with the mass of the Sun
The volume of the material that must be used to make a star with the mass of the sun is 1.2×10⁵¹ m³.
What is volume?Volume is the amount of space occupied by an object or a plane figure.
To calculate the volume of the material that must be used to make a star with the mass of the sun, we use the formula below.
Formula:
D = m/V............ Equation 1Where:
D = Density of the interstellar gasm = mass of the sunV = Volume of the materialMake V the subject of the equation
V = m/D........... Equation 2From the question,
Given:
m = mass of the sun = 1.9891×10³⁰ kgD = 1 atom/cm³ = 1.66×10⁻²¹ kg/m³Substitute these values into equation 2
V = ( 1.9891×10³⁰)/(1.66×10⁻²¹)V = 1.2×10⁵¹ m³Hence, The volume of the material that must be used to make a star with the mass of the sun is 1.2×10⁵¹ m³.
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If the force generated by the car to push it forward is 8,000 N, what can be said about the force opposing the car’s motion?
According to Newton's third law
Ever action has a equal and opposite reaction.So
[tex]\\ \rm\dashrightarrow F_{A}=-F_A[/tex]
Hence if applied force is 8000N opposing force is also 8000NAs car is pushed forward so the opposing force is less than 8000N
Answer:It is less than 8,000 N and greater than zero.
Explanation:
a right angled triangle has 5cm opposite side, 9cm adjacent side. find length of hypotunise
Hypotenuse be H
Apply Pythagorean theorem
[tex]\\ \sf\Rrightarrow H^2=P^2+B^2[/tex]
[tex]\\ \sf\Rrightarrow H^2=5^2+9^2[/tex]
[tex]\\ \sf\Rrightarrow H^2=25+81[/tex]
[tex]\\ \sf\Rrightarrow H^2=106[/tex]
[tex]\\ \sf\Rrightarrow H=\sqrt{106}cm[/tex]
why some aqutatic plants float an water give reason science subjects class 4
A disk of radius a has a total charge Q uniformly distributed over its surface. The disk has negligible thickness and lies in the xy plane.
What is the electric potential V(z) on the z axis as a function of z , for z>0 ?
What is the magnitude E of the electric field on the z axis, as a function of z , for z>0 ?
The electric potential V(z) on the z-axis is : V = [tex](\frac{Q}{a^2} ) [ (a^2 + z^2)^{\frac{1}{2} } -z[/tex]
The magnitude of the electric field on the z axis is : E = kб 2[tex]\pi[/tex]( 1 - [z / √(z² + a² ) ] )
Given data :
V(z) =2kQ / a²(v(a² + z²) ) -z
Determine the electric potential V(z) on the z axis and magnitude of the electric fieldConsidering a disk with radius R
Charge = dq
Also the distance from the edge to the point on the z-axis = √ [R² + z²].
The surface charge density of the disk ( б ) = dq / dA
Small element charge dq = б( 2πR ) dr
dV [tex]\frac{k.dq}{\sqrt{R^2+z^2} } \\\\= \frac{k(\alpha (2\pi R)dR}{\sqrt{R^2+z^2} }[/tex] ----- ( 1 )
Integrating equation ( 1 ) over for full radius of a
∫dv = [tex]\int\limits^a_o {\frac{k(\alpha (2\pi R)dR)}{\sqrt{R^2+z^2} } } \,[/tex]
V = [tex]\pi k\alpha [ (a^2+z^2)^\frac{1}{2} -z ][/tex]
= [tex]\pi k (\frac{Q}{\pi \alpha ^2})[(a^2 +z^2)^{\frac{1}{2} } -z ][/tex]
Therefore the electric potential V(z) = [tex](\frac{Q}{a^2} ) [ (a^2 + z^2)^{\frac{1}{2} } -z[/tex]
Also
The magnitude of the electric field on the z axis is : E = kб 2[tex]\pi[/tex]( 1 - [z / √(z² + a² ) ] )
Hence we can conclude that the answers to your question are as listed above.
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Which of the following can only be a situation of increasing temperature?
1. The phase change of the material is going from water to solid
2. The height of the object is increasing
3. The objects speed in increasing at a constant rate
4. The average kinetic energy of the particles of a material is increasing
Increasing the temperature causes an increase in the average kinetic energy of the particles of a material.
What is average kinetic energy of particles?The average kinetic energy of particles is the energy possessed by particles due to their constant motion.
The constant motion of particles occurs due to the energy acquired by the particles, when the temperature of the particles increases, the average kinetic energy increases which in turn increases the speed of the particles.
Thus, we can conclude that, increasing the temperature causes an increase in the average kinetic energy of the particles of a material.
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Where is the electric field between a charged balloon and a charged piece of paper 0.04 m away?
A. The electric field is in the region around the balloon and paper where there are outside charges that affect them.
B. The electric field is in the 0.04 m distance between the balloon and paper and not anywhere else around either the paper or the balloon.
C. The electric field is all around the balloon and paper including between them, where, depending on their charge, there would be a force of either attraction or repulsion.
D. The electric field is in the region in which the forces come in contact.
The electric field is all around the balloon and paper including between them, where, depending on their charge, there would be a force of either attraction or repulsion.
What is electric field?An electric field is the physical field that surrounds electrically charged particles and exerts force on all other charged particles in the field, either attracting or repelling them.
Thus, for the charged balloon and a charged piece of paper 0.04 m away, we can conclude that, the electric field is all around the balloon and paper including between them, where, depending on their charge, there would be a force of either attraction or repulsion.
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The frictional force between two surfaces at rest depends on which of the following?
Answer:
the two types of materials interacting (described by the coefficient μk) and how hard these two surfaces are pushed together (the normal force)
hope this helps and is it needs more let me know
A boy stands 190m from a high wall and claps his hands,if he hears an echo 1.3 seconds later. calculate the speed of sound in air.
Answer:
292.31 m/s
Explanation:
If Distance (d) = 190m
Time (t) = 1.3s
Speed of sound in air (v) =?
then
2d=vt
v=2d/t
v= 2×190/1.3
v=292.31 m/s
.
A
saloon car starting from rest will accelerates
to velocity of 48 km/h in 10 seconds. calculate
the
aceleration-
What’s the answer ?
Answer:
47
Explanation:
48km:1hr (10sec×60min=600hr)
¥ :600hr
1hr÷¥=1. 48×600÷1=2800
2800÷60=47
47 will be the acceleration
[tex]\text{Initial velocity,}~ u = 0 ~ ms^{-1}\\\\\text{Final velocity,}~ v = 48~kmh^{-1} = \dfrac{48\times 1000}{3600} ms^{-1} = 13.33 ms^{-1}\\ \\\text{Time,}~ t = 10~ sec\\\\\text{Acceleration,}~ a = \dfrac{v-u}{t} = \dfrac{13.33-0}{10} = \dfrac{13.33}{10} = 1.33 ~ ms^{-2}\\\\\text{Hence the acceleration of the car is}~ 1.33 ~ms^{-2}.[/tex]
A circular ferris wheel that revolves at a constant rate once every 30 seconds. The
radius of the ferris wheel is 10 m. What is the normal force of the ferris wheel on a 10
kg toddler at the very bottom of the ferris wheel?
The normal force of the ferris wheel on a 10kg toddler at the very bottom of the ferris wheel is 102.41 N.
Centripetal force of the Ferris wheelThe normal force of the ferris wheel on a 10kg toddler at the very bottom of the ferris wheel is calculated as follows;
Fn = Fc + mg
Fn = mω²r + mg
where;
ω is the angular speed = 1 rev/30 s = 2π/30 s = 0.21 rad/sFn = 10(0.21²) 10 + 10(9.8)
Fn = 102.41 N
Thus, the normal force of the ferris wheel on a 10kg toddler at the very bottom of the ferris wheel is 102.41 N.
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