Answer:
(a) Q = 142.67 W
(b) Basal Metabolic Rate = 178.33 W
Explanation:
(a)
We can find the heat radiated by the person by using Stefan-Boltzman's law:
[tex]Q = \sigma A (T^4 - T_{s}^4)\\[/tex]
where,
Q = heat radiated per second = ?
σ = Stefan-Boltzman Constant = 5.6703 x 10⁻⁸ W/m².k⁴
A = Surface Area = 2 m²
T = Temperature of Skin = 30° C + 273 = 303 k
Ts = Temperature of room = 18° C +273 = 291 k
Therefore,
[tex]Q = (5.6703\ x\ 10^{-8}\ W/m^2.k^4)(2\ m^2)[(303\ k)^4-(291\ k)^4][/tex]
Q = 142.67 W
(b)
Since the heat calculated in part (a) is 80 percent of basal metabolic rate. Therefore,
[tex]Q = (0.8)(Basal\ Metabolic\ Rate)\\Basal\ Metabolic\ Rate = \frac{Q}{0.8}\\\\Basal\ Metabolic\ Rate = \frac{142.67\ W}{0.8}[/tex]
Basal Metabolic Rate = 178.33 W
(a) The excess heat just through radiation Q = 142.67 W
(b) Basal Metabolic Rate = 178.33 W
What is metabolic rate?Basal metabolic rate is the number of calories your body needs to accomplish its most basic (basal) life-sustaining functions.
(a) We can find the heat radiated by the person by using Stefan-Boltzman's law:
[tex]Q=\sigma A(T^4-T_s^4)[/tex]
where,
Q = heat radiated per second = ?
σ = Stefan-Boltzman Constant = 5.6703 x 10⁻⁸ W/m².k⁴
A = Surface Area = 2 m²
T = Temperature of Skin = 30° C + 273 = 303 k
Ts = Temperature of room = 18° C +273 = 291 k
Therefore,
[tex]Q=(5.6703\times 10^{-8}\times (2)\times[(303)-(291)][/tex]
Q = 142.67 W
(b) Since the heat calculated in part (a) is 80 percent of basal metabolic rate. Therefore,
[tex]\rm Q=0.8\times (Basal\ Metabolic\ Rate)[/tex]
[tex]\rm Basal\ metabolic \ Rate = \dfrac{Q}{0.8}[/tex]
[tex]\rm Basal\ Metabolic\ Rate = \dfrac{142.67}{0.8} =178.330W[/tex]
Basal Metabolic Rate = 178.33 W
Hence the excess heat just through radiation Q = 142.67 and Basal Metabolic Rate = 178.33 W
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I need help plissss..............
Consider the path of a comet orbiting a star, the system of the comet plus the star. Which of the following statements are correct? Select all that are True. 1) As the comet slows down, the kinetic energy of the system decreases. 2) As the comet's kinetic energy increases, the gravitational potential energy of the system also increases. 3) External work must be done on the system to speed up the comet. 4) As the kinetic energy of the system increases, the gravitational potential energy of the system decreases. 5) As the comet slows down, energy is lost from the system.
Answer:
True 1, 4
False 2, 3, 5
Explanation:
The system is formed by the Sun that is fixed at a point (focus of movement) and the comet that rotates around in styptic orbits. The only force involved is the force of attraction between the two bodies, if we write the energy of the system
Em = K + U
Em = ½ m v2 + G m Ms / r2
where m is the mass of the comet, Ms the mass of the Sun and r the distance between them.
This system is isolated so the energy is conserved throughout the movement, it only transforms from kinetic to gravitational potential.
Let's review the different claims;
1) True. The speed of the comet determines its kinetic energy, so when decreasing the speed decreases the kinetic energy, there is also a decrease due to the lost mass
2) False. The total energy is constant, so if the kinetic energy increases, the power energy must decrease
3) False. The comet's speed changes are due to changes in gravitational energy, so no external work is needed to change the speed.
4) True. Correct because the sum of the two must be constant
5) False. When the comet loses speed, the energy increases, the power would gravitate, so there is no loss of energy, we are ignoring the loss of mass of the comet.
A vibrating mass of 300 kg mounted on a massless support by a spring of stiffness 40,000 N>m and a damper of unknown damping coefficient is observed to vibrate with a 10-mm amplitude while the support vibration has a maximum amplitude of only 2.5 mm (at resonance). Calculate the damping constant and the amplitude of the force on the base.
Answer:
400 N
Explanation:
[tex]\text { Given: } m=300 \mathrm{~kg}, k=40,000 \mathrm{~N} / \mathrm{m}, \omega_{b}=\omega_{n}(r=1), X=10 \mathrm{~mm}, Y=2.5 \mathrm{~mm}[/tex] .
Find damping constant
[tex] \frac{X}{Y}=\left[\frac{1+(2 \zeta r)^{2}}{\left[\left(1-r^{2}\right)^{2}+(2 \zeta r)^{2}\right.}\right]^{1 / 2} \\ \left.\frac{10}{2.5}=\frac{\left\lceil 1+4\zeta^{2}\right]^{1 / 2}}{4 \zeta^{2}}\right] \\ 16=\frac{1+4 \zeta^{-2}}{4 \zeta^{2}} \\ \zeta^{2}=\frac{1}{60}=\frac{c^{2}}{4 k m} \\ c=\sqrt{\frac{4(40,000)(300)}{60}} \\ c=894.4 \mathrm{~kg} / \mathrm{s}[/tex]
Amplitude of force on base:
[tex]F_{T}=k Y r^{2}\left[\frac{1+(2 \zeta r)^{2}}{\left(1-r^{2}\right)^{2}+(2 \zeta r)^{2}}\right]^{1 / 2}[/tex]
substituting the values in above formula we get
F_T = 400 N
Two identical positive charges exert a repulsive force of 6.4x10^-9 N when separated by a distance of 3.8x10^10 m. Calculate the charge of each.
Answer:F = kq2/d2 ⇒
q = √(Fd2/k)
q = d √(F/k)
d = 3.8 x 10-10 m
F = 6.4 x 10-9 N
Look up k in your physics book in appropriate units, and plug in the numbers. You should get q in coulombs.
Explanation:
The value of each charge will be 1.64 ×10⁻⁴. The concept of the columb force is used.
What is the charge?When the matter is put in an electromagnetic field, it has an electric charge, which causes it to experience a force. A positive or negative electric charge can exist.
Charges that are similar repel each other, whereas charges that are dissimilar attract each other. The term "neutral" refers to an item that has no net charge.
[tex]\rm F =K \frac{q_1Q_2}{d^2} \\\\ F = K\frac{q^2}{d^2} \\\\ q = \sqrt{\frac{dF}{k} } \\\\ q = \sqrt{\frac{3.8 \times 10^{10}\times 6.4 \times 10^{-9}}{9 \times 10^9} } \\\\ q=1.64 \times 10-4[/tex]
Hence the value of each charge will be 1.64 ×10⁻⁴. The concept of the columb force is used.
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The modern model of the atom describes electrons in a little less specific detail than earlier models did. Why is it that being less sure about the placement of electrons in an atom is actually an improvement over earlier models?
The plum pudding model of the atom states that
Answer:
It is because one cannot know exactly the position of the electron within the atom.
One formulation of Heisenberg's Uncertainty Principle tells us that one cannot know simultaneously the position and momentum of the electron, so one cannot specify exactly either coordinate because the other would be infinite.
Bohr specified the most probable position of the electron at its lowest energy level in hydrogen and the product of the two would be about the Heisenberg value.
a potted plant falls from a window sill and is gaining speed. which one of the following statements is true of the plant?
a) its kinetic energy is constant
b) its kinetic energy is increasing
c) its kinetic energy is decreasing
A car is travelling at 15 m/s on a horizontal road and stopped after 4 s. The coefficient of kinetic friction between the tires and road is:
Answer:
Fr,= umg
umg= ma
a= v/t
umg= mv/t
u= v/gt= 0.38
18. Write conversion factors (as ratios) for the number of:
(a) yards in 1 meter
(b) liters in 1 liquid quart
(c) pounds in 1 kilogram
Answer:
Conversion tables show:
1 m = 1.09361 yds
1 Lit = .26418 gal = 1.05672 qt or 1 qt = .944632 Lit
1 lb = .45359 kg = 2.2046 Lbs / Kg
So X yds = X m * 1.09361 yds / m = 1.09361 * X yds
Likewise X Lit = X qt / 1.05672 qt/ Lit = X / 1.05672 Lit = .94632 X Lit
So X Lbs = X kg * 2.2046 Lbs / Kg = 2.2046 Lbs
The total charge a battery can supply is rated in mA⋅hmA⋅h, the product of the current (in mA) and the time (in h) that the battery can provide this current. A battery rated at 1000mA⋅h can supply a current of 1000 mA for 1.0 h, 500 mA current for 2.0 h, and so on. A typical AA rechargeable battery has a voltage of 1.2 V and a rating of 1800mA⋅h. For how long could this battery drive current through a long, thin wire of resistance22Ω?
Answer:
118800 seconds
Explanation:
Given :
Voltage, V = 1.2 V
Resistance, R = 22 Ω
Applying Ohm's law, we get
Voltage, V = IR
Current [tex]$I=\frac{V}{R}$[/tex]
[tex]$I=\frac{1.2}{22}$[/tex]
I = 0.0545 A
Rate = 1800 mAh
Time taken, [tex]$t=\frac{1800 \times 10^{-3}}{0.0545}$[/tex]
= 33 hr
= 118800 s
Which of the following represents a concave lens?
A. -di
B. +di
C. -f
D. +f
Answer:
The answer is option D. +f
Option D represents a concave lens. There are two types of lenses, one is a concave lens while the other is the convex lens.
What is the definition of a concave lens?A concave lens deviates a direct beam from the source into a reduced form. At minimum, one interior face of concave lenses is curved.
Because it is curved round inwards at the center and bulges outwards through the edges, causing the light to diverge, a concave lens is also known as a diverging lens.
It forms an upright , virtual picture both real and virtual pictures are formed from the concave lens.
The image formed from the positive side of the focus of the lens.+f shows the positive side of the focus of the lens.f is the focal length.
Hence, option D represents a concave lens
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a man pushed on the side ..
Answer:
B.will increase the maximum static friction between the box and the floor
Explanation:
Because static friction is the force that keeps an object at rest
There are two main types of collisions that you will study: elastic and perfectly inelastic. In an elastic collision, kinetic energy is conserved. In a perfectly inelastic collision, the particles stick together and thus retain the same velocity after the collision.
a. True
b. False
Answer:
The first part is right (KE is conserved in an elastic collision).
The second part of the statement is false,.
Since momentum is conserved, let moving mass m strike stationary mass M:
m v = (m + M) V where m v is the momentum in
Obviously, v does not equal V.
how is a trench and a tsunami related? 6-8 sentences
Answer: A tsunami is a very long-wavelength wave of water that is generated by sudden displacement of the seafloor or disruption of any body of standing water. Tsunami are sometimes called "seismic sea waves", although they can be generated by mechanisms other than earthquakes. Tsunami have also been called "tidal waves", but this term should not be used because they are not in any way related to the tides of the Earth. Because tsunami occur suddenly, often without warning, they are extremely dangerous to coastal communities. Ocean trenches are steep depressions in the deepest parts of the ocean [where old ocean crust from one tectonic plate is pushed beneath another plate, raising mountains, causing earthquakes, and forming volcanoes on the seafloor and on land.
Explanation:
Compare and contrast the solar eclipse seen in this video to a lunar eclipse.
Answer: sadly, I can’t see the video. However, a lunar eclipse happens when the moon is hidden by the earth’s shadow. A solar eclipse occurs when the moon casts a shadow on the earth.
Explanation: I’m not completely sure if this is what you were looking for, but I hope it helps anyway.
Which of the following is an example of predation?
Answer:
an owl hunts, catches, and consumes a field mouse for energy
Explanation:
Please help. It’s probably easy
What is energy transfer in a car crash
Force energy- kinetic energy
Answer:
Kinetic and thermal
Explanation:
Kinetic because a moving car is transferring movement energy into the other one. Thermal because, in a car crash, the touching surfaces of both cars friction and that produces heat.
Riders in an amusement park ride shaped like a Viking ship hung from a large pivot are rotated back and forth like a rigid pendulum. At each end of the swing the ship hangs motionless for a moment before the ship swings down under the influence of gravity. Assume that this motionless point occurs when the bar connecting the pivot point and the ship is horizontal.
Required:
a. Assuming negligible friction, find the speed of the riders at the bottom of its arc, given the system's center of mass travels in an arc having a radius of 14.0 m and the riders are near the center of mass.
b. What is the centripetal acceleration at the bottom of the arc?
c. Draw a free body diagram of the forces acting on a rider at the bottom of the arc.
d. Find the force exerted by the ride on a 60.0 kg rider and compare it to her weight.
e. Discuss whether the answer seems reasonable.
Answer:
a) v = 16.57 m / s, b) a = 19.6 m / s², d) N = 1.76 10³ N, N / W = 3
Explanation:
This exercise looks interesting, but I think you have some problem with the writing, the questions seem a bit disconnected from the initial text.
Let's answer the questions.
a) For this part we can use energy considerations.
Starting point. The upper part of the trajectory indicates that the arm is horizontally
Em₀ = U = m g h
in this case h = r
Final point. For lower of the trajectory
Em_f = K = ½ m v²
as they indicate that there is no friction
Em₀ = em_f
mgh = ½ m v²
v = [tex]\sqrt{2gh}[/tex]
let's calculate
v = [tex]\sqrt{2 \ 9.8 \ 14.0}[/tex]
v = 16.57 m / s
b) the centripetal acceleration has the formula
a = v² / r
a = 16.57² / 14.0
a = 19.6 m / s²
c) see attached where the diagram is
where N is the normal and w the weight
d) let's use Newton's second law
N-W = m a
N - mg = m ar
N = m (g + a)
let's calculate
N = 60.0 (9.8 + 19.6)
N = 1.76 10³ N
the relationship with weight is
N / W = 1.76 10³/( 60 9.8)
N / W = 3
normal is three times greater than body weight
e) the answer is reasonable since by Newton's first law the body must continue in a straight line, therefore to change its trajectory a force must be applied to deflect it
What speed must a 600 kg car have in order to have the same momentum as a 1200 kg truck traveling at a velocity of 10 m/s to the west? 5 m/s west B 20 mls west 5 m/s east 20 m/s east
A) 5m/s west
B) 20m/s west
C) 5m/s east
D) 20m/s east
Answer:
20 m/s
Explanation:
How can parents help children to gain friends?
Answer:
You could try finding a familiar peer to join the activity with your child. Or ask your child who their friends are at school, or what they look for in a friend at school.
Answer:
Let the parents their Children to play outside
Explanation:
I HOPE I HELP YOU
Unless otherwise stated, all objects are located near the Earth's surface, where g = 9.80 m/s2 .
A force acts on a 1.5 kg , mass, giving it an acceleration of 3.0 m/s2 .
1. If the same force acts on a 3.0 kg mass, what acceleration would be produced?
2. What is the magnitude of the force?
Answer:
1) 1.5 m/s^2
2) 4.5 N
Explanation:
From Newton's Second Law of motion, we know
[tex]F=m*a[/tex]
Which states that to calculate the force acting on an object, you multiply its mass and acceleration.
So, we know an object of mass 1.5 kg has an acceleration of 3 m/s^2, then
[tex]F=m*a=1.5*3=4.5[/tex]
A force of 4.5 N is acting on the object.
If a force of 4.5 N acts on a mass of 3kg we have
[tex]a=\frac{F}{m}=\frac{4.5}{3}=1.5[/tex]
So, it would give it an acceleration of 1.5 m/s^2.
An amateur blacksmith wants to cool off a 42kg glowing piece of iron, specific heat 470and decides to toss it into a 5.0 kg iron bucket with 10.0 kg of room temperature(23 C) water in it. To his surprise the water completely evaporates away (meaning once it vaporizes it is no longer part of the system) and after some time he goes to pick up the bucket but finds that the bucket is at 150 C.
Required:
What was the initial temperature of the glowing piece of iron?
Answer:
The right approach is "1479°C".
Explanation:
The given values are:
Mass of iron piece,
[tex]m_p=42 \ kg[/tex]
Mass of iron bucket,
[tex]m_I=5 \ kg[/tex]
Mass of water,
[tex]m_w=10 \ kg[/tex]
Iron's specific heat,
[tex]C_I=470 \ J/Kg^{\circ}C[/tex]
Water's specific heat,
[tex]C_w=4186 \ J/Kg^{\circ}C[/tex]
Initial temperature,
[tex]t_I=23^{\circ}C[/tex]
Final equilibrium temperature,
[tex]T=150^{\circ}C[/tex]
Latent heat,
[tex]L_v=2260\times 10^3 \ J/Kg[/tex]
As we know,
The heat lost by the glowing piece of iron will be equal to the heat gain by the iron bucket as well as water, then
⇒ [tex]m_IC_I \Delta T=m_wC_w(100-23)+m_wL_v+m_bC_I(150-23)[/tex]
On substituting the given values, we get
⇒ [tex]42\times 420\times \Delta T=10\times 4186(100-23)+10(2260\times 10^3)+5\times 420(150-23)[/tex]
⇒ [tex]17640 \Delta T=3.22\times 10^6+2.26\times 10^7+2.667\times 10^5[/tex]
⇒ [tex]\Delta T=\frac{2.60867\times 10^7}{17640}[/tex]
⇒ [tex]\Delta T=1479^{\circ}C[/tex]
What is a energy transformation when using a microwave to make popcorn?
Answer:
Radiation
Explanation:
Radiant energy
Explanation:
Radiant energy is transformed into thermal energy as the popcorn kernels absorb the microwaves. This causes the kernels to become hot and pop. Electric energy is transferred from the electrical outlet to the microwave.
Cartesian coordinate system is used for?
Answer:
sorry not sure but i can try help with telling you this...
Explanation:
alls you havs to do is ask the internet and it will tell you
Can I please have help
Answer:
it will usually increase
Explanation:
potato
a solid disk rotates in the horizontal plane at an angular velocity of 4.9 x 10 rad/s with respect to an axis perpendicular to the disk at its center the moment of inertia of the disk is 0.14 kg from above sand is dropped straight down onto this rotating disk so that a thin unifrom ring of sand is formed at distance of 0.4 m from the axis the sand in the ring has mass of 0.5 kg after all the sand is in place what is the angular velocity of the disk
Answer:
ωf = 3.1*10 rad/sec
Explanation:
Assuming no external torques acting while the sand is being dropped, total angular momentum must keep constant.So we can write the following equality:[tex]L_{o} = L_{f} (1)[/tex]
For a rigid body rotating with respect to an axis, the angular momentum can be written as follows:[tex]L = I* \omega (2)[/tex]
where I = moment of inertiaω = angular velocityReplacing (2) on both sides of (1) we get:[tex]I_{o}* \omega_{o} = I_{f}* \omega_{f} (3)[/tex]
In (3) we know the values of I₀ and ω₀ (since they are givens), but we need to find the value of If first.The final moment of inertia, will be equal to the sum of the initial one, plus the one due to the ring of sand, that also rotates with respect to an axis perpendicular to the disk, as follows:[tex]I_{f} = I_{o} + I_ {ring} (4)[/tex]The moment of inertia of a circular ring is as follows:[tex]I_{ring} = m_{ring} *r^{2} (5)[/tex]
Replacing by the givens in (5) we get:[tex]I_{ring} = m_{ring} *r^{2} = 0.5 kg * (0.4m)^{2} = 0.08 kg*m2 (6)[/tex]
Replacing (6) in (4):[tex]I_{f} = I_{o} + I_ {ring} = 0.14kg*m2 + 0.08 kg*m2 = 0.22 kg*m2 (7)[/tex]Replacing I₀, ω₀ and If in (3), we can solve for ωf, as follows:[tex]\omega_{f} =\frac{I_{o} *\omega_{o} }{I_{f} } = \frac{0.14kg*m2*4.9*10rad/sec}{0.22kg*m2} = 3.1*10 rad/sec (8)[/tex]D
If you increase the
frequency of a
wave, what
happens to the
speed?
G
A. It decreases.
B. It stays the same.
C. It increases.
D. It can increase or decrease.
Answer:
D
Explanation:
I think you got it right
Please help me !!!!!!!
Answer: I believe that it is 35 Joules.
Explanation:
100 - 65 = 35
:)
Which planet is least like earth? Mars,Venus, or Jupiter
Answer:
mars, reason why is because they both are diff from the size
Explanation:
Please help !!!!!!!!!!!!
Answer:
152 Volts
Explanation:
First, the Resistors are in series. So, the net resistance, R = 3 + 4 +3 + 4 +5
= 19 ohms
Using, V = IR;
V (the needed P.D) = 8 x 19 = 152 Volts
will be needed to successfully transport 8 amps of current round the circuit
Answer:
4q
Explanation:
wait nvm i dont know