Answer:
Weightlessness
Explanation:
When the elevator is in free fall, this can only occur when the cord of the elevator breaks.
The acceleration of the elevator will be equal to the acceleration due to gravity. That is:
a = g
Then, the body will experience what we called WEIGHTLESSNESS
Where the normal reaction N of the person will tend to zero. That is
N = 0
The value of FN < 0 because the person inside the lift will experience weightlessness.
As a rough model of the impact of walking/running, consider that half the mass of the body falls from a height of 4.77-cm onto a single foot. (During a typical stride, an adult's center-of-mass moves approximately this distance vertically). Use the kinematic equations to calculate the speed of an object falling from this height at the moment of impact with the ground under the influence of gravity.A. As a rough model of the impact of walking, consider that half of the mass of the entire body strikes the ground with a downward velocity of 1.0 m/s and comes to a full vertical stop over an impact duration of 20 ms. Calculate the force associated with this single step for a person with a mass of 74.2 kg. B. Calculate the stress (solid pressure) of a force of 1880 N applied across the 0.4 cm^2 cross-sectional area of the typical Achilles tendon. For reference, the maximum rupture stress of tendons has been reported in the range of 100-150 MPa.
Answer:
0.967 m/s
1855 N
[tex]46.375\ \text{MPa}[/tex]
Explanation:
v = Final velocity
u = Initial velocity = 0
s = Displacement = 4.77 cm
g = a = Acceleration due to gravity = [tex]9.81\ \text{m/s}^2[/tex]
From the kinematic equations
[tex]v^2-u^2=2as\\\Rightarrow v=\sqrt{2as+u^2}\\\Rightarrow v=\sqrt{2\times 9.81\times 0.0477+0}\\\Rightarrow v=0.967\ \text{m/s}[/tex]
The velocity of the object at the moment of impact is 0.967 m/s
Now
[tex]\Delta v[/tex] = Change in velocity = 1 m/s
t = Time taken = 20 ms
m = Half mass of the person = [tex]\dfrac{74.2}{2}=37.1\ \text{kg}[/tex]
[tex]F=\dfrac{m}{t}\\\Rightarrow F=\dfrac{37.1\times 1}{20\times 10^{-3}}\\\Rightarrow F=1855\ \text{N}[/tex]
The force associated with a single step of the person is 1855 N
A = Area = [tex]0.4\ \text{cm}^2[/tex]
Stress is given by
[tex]\sigma=\dfrac{F}{A}\\\Rightarrow \sigma=\dfrac{1855}{0.4\times 10^{-4}}\\\Rightarrow \sigma=46375000\ \text{Pa}=46.375\ \text{MPa}[/tex]
The stress on the tendon is [tex]46.375\ \text{MPa}[/tex]
The speed of object during falling is 0.967 m/s.
(A) The magnitude of force associated with this single step for a person is 1855 N.
(B) The required value of stress at tendons is [tex]4.70 \times 10^{7} \;\rm Pa[/tex].
Given data:
The height of fall is, h = 4.77 cm = 0.0477 m.
The magnitude of downward velocity is, v' = 1.0 m/s.
The duration of impact is, [tex]t = 20 \;\rm ms =20 \times 10^{-3} \;\rm s[/tex].
The mass of person is, m = 74.2 kg.
The magnitude of force is, F' = 1880 N.
The cross-sectional area is, [tex]A =0.4 \;\rm cm^{2} = 0.4 \times 10^{-4} \;\rm m^{2][/tex].
The problem has several parts using different concepts. First obtain the final speed of object to fall by using the second kinematic equations of motion as,
[tex]v^{2}=u^{2}+2gh[/tex]
Solving as,
[tex]v^{2}=0^{2}+(2 \times 9.8 \times 0.0477)\\\\v = \sqrt{(2 \times 9.8 \times 0.0477)} \\v = 0.967 \;\rm m/s[/tex]
Thus, the speed of object during falling is 0.967 m/s.
(A)
Now coming to next part, the half of mass means, m' = m/2 = 74.2/2 = 37.1 kg.
Apply the expression of average force as,
[tex]F =\dfrac{m'v'}{t}[/tex]
Solving as,
[tex]F =\dfrac{37.1 \times 1}{20 \times 10^{-3}}\\\\F = 1855 \;\rm N[/tex]
Thus, the magnitude of force associated with this single step for a person is 1855 N.
(B)
The expression for the stress is given as,
[tex]\sigma = \dfrac{F'}{A}[/tex]
Solving as,
[tex]\sigma = \dfrac{1880}{0.4 \times 10^{-4}}\\\\\sigma =4.70 \times 10^{7} \;\rm Pa[/tex]
Thus, the required value of stress at tendons is [tex]4.70 \times 10^{7} \;\rm Pa[/tex].
Learn more about the Stress force here:
https://brainly.com/question/18274389
A series RCL circuit contains a 65.2-Ω resistor, a 2.26-μF capacitor, and a 2.08-mH inductor. When the frequency is 2400 Hz, what is the power factor of the circuit?
Answer:
The power factor of the circuit is 0.99
Explanation:
Given;
resistance of the resistor, R = 65.2 ohms
capacitance of the capacitor, C = 2.26 μF = 2.26 x 10⁻⁶ F
inductance, L = 2.08 mH = 2.08 x 10⁻³ H
frequency of the AC, f = 2400 Hz
The angular frequency is given by;
ω = 2πf
ω = 2π(2400) = 15081.6 rad/s
The inductive reactance is given by;
XL = ωL
XL = (15081.6 x 2.08 x 10⁻³)
XL = 31.37 ohms
The capacitive reactance is given by;
[tex]X_c = \frac{1}{\omega C} \\\\X_c = \frac{1}{(15081.6)(2.26*10^{-6} )}\\\\X_c = 29.34 \ ohms[/tex]
The phase difference is given by;
[tex]tan\phi = \frac{X_l - X_c}{R}\\\\ tan\phi =\frac{31.37-29.34}{65.2} \\\\tan\phi = 0.0311 \\\\\phi = tan^{-1} (0.0311)\\\\\phi = 1.78^0[/tex]
The power factor is given by;
CosФ = Cos(1.78) = 0.99
Therefore, the power factor of the circuit is 0.99
A sample contains 20 kg of radioactive material. The decay constant of the material is 0.179 per second. If the amount of time that has passed is 300 seconds, how much of the of the original material is still radioactive? Show all work
Answer:
6,000 kg
Explanation:
there’s a tornado warning where i live rn
Answer:
same
Explanation:
aww good luck, i hope u n ur family turn out okkk
what transition metal has 5 more protons than the halogen found in period 3?
Answer: Titanium (Ti)
Explanation:
First, each element has a unique atomic number Z, that is equal to the number of protons in the nucleus.
The halogen in period 3 is chlorine (Ch)
Chlorine's atomic number is Z = 17, this means that it has 17 protons.
Now we want to find a transition metal that has 5 more protons, then this transition metal has Z = 17 + 5 = 22
Now we can look at the periodic table and find the element with Z = 22, and if this is in the d-block, then this will be a transition metal.
The element with Z = 22 is titanium (Ti)
You wish to design a pendulum which moves a mass along an arc of length 40 cm when the angle with the vertical changes by 20 degrees. What should be the length L in meters of the pendulum? Enter the numerical answer without units. Your answer must be within 5% of the exact answer to receive credit.
Answer:
The length of the pendulum cord is approximately 114.592 centimeters.
Explanation:
We include a representation of the motion of the pendulum in the image attached below. The trajectory described by the pendulum is represented by the following geometrical expression:
[tex]s = \theta \cdot r[/tex] (1)
Where:
[tex]\theta[/tex] - Angular change with the vertical, measured in radians.
[tex]r[/tex] - Length of the pendulum cord, measured in centimeters.
[tex]s[/tex] - Arc, measured in centimeters.
If we know that [tex]\theta = \frac{\pi}{9}[/tex] and [tex]s = 40\,cm[/tex], then the length of the pendulum cord is.
[tex]r = \frac{s}{\theta}[/tex]
[tex]r = \frac{40\,cm}{\frac{\pi}{9} }[/tex]
[tex]r \approx 114.592\,cm[/tex]
The length of the pendulum cord is approximately 114.592 centimeters.
The time constant for RC circuit with the values of R1 and C1 is 5ms. What will be the time constant for a new RC circuit with the values: R2=10R1 and C2 = 0.5C1.
a. 2.5ms
b. 15.5ms
c. 50ms
d. 25ms
e. 15ms
Answer:
d. 25 ms
Explanation:
In a RC circuit we call time constant to the product of the resistance times the capacitance, which represents the time when the charge reaches to the 63% of the final value, as follows:[tex]\tau_{1} = R_{1} *C_{1} = 5 ms (1)[/tex]
If we have a new circuit with new values for R and C, the time constant will be defined in the same way, as follows:[tex]\tau_{2} =10* R_{1} *0.5*C_{1} = 5*(R_{1}* C_{1}) = 5* \tau_{1} = 5* 5 ms = 25 ms (2)[/tex]
When lightning occurs, it produces a sound wave and a light wave at the same exact time. If u are watching a faraway storm, which wave gets to you first?
why does sound energy even exist
The displacement of a transvers wave travelling on a string is represented by D1 = 4.2sin(0.84.x - 47t + 21) where D1 and x are in cm and t in s.Find an equation that represents a wave which, when traveling in the opposite direction, will produce a standing wave when added to this one
Answer:
The equation for such type of wave is [tex]D_2 = sin(0.84.x + 47t + 21)[/tex]
Explanation:
From the question we are told that
The displacement is [tex]D_1 = 4.2sin(0.84.x - 47t + 21)[/tex]
Here the wave number is k= 0.84
The angular frequency is [tex]w = 47[/tex]
The phase shift is [tex]\phi = 21[/tex]
Generally the equation that represents a wave which, when traveling in the opposite direction, will produce a standing wave when added to this one is mathematically represented as
[tex]D_2 = sin(0.84.x + 47t + 21)[/tex]
What frequency is received by a person watching an oncoming ambulance moving at 115 km/h and emitting a steady 753 Hz sound from its siren
Answer:
77.6 Hz
Explanation:
What frequency is received by a person watching an oncoming ambulance moving at 115 km/h and emitting a steady 753 Hz sound from its siren.
The given parameters are:
Observer speed = 115 km/h
Source frequency = 753 Hz
Speed of sound = 342 m/s
First convert km/h to m/s
Observer speed = (115 × 1000) / 3600
Observer speed = 31.94 m/s
The frequency received by the person will be:
F = fv / ( V - v )
Where
F = frequency received by the person
f = siren frequency
V = speed of sound
v = speed of the ambulance
Substitute all the parameters into the formula
F = (753 × 31.94) / ( 342 - 31.94 )
F = 24050.82 / 310.06
F = 77.568 Hz
Therefore, the frequency received by a person is approximately 77.6Hz
A container is filled to a depth of 21.0 cm with water. On top of the water floats a 35.0-cm-thick layer of oil with specific gravity 0.600. What is the absolute pressure at the bottom of the container
Answer:
P_abs = 105120.2 N/m²
Explanation:
We are given;
Specific gravity of oil; ρ_oil = 0.6 g/cm³ = 600 kg/m³
Depth of water; h_w = 21 cm = 0.21 m
Depth of oil; h_o = 35 cm = 0.35 m
From tables specific gravity of water is; ρ_w = 1000 kg/m³
Thus, to get the absolute pressure at the bottom of the container, we will use the formula;
P_abs = (ρ_w × g × h_w) + (ρ_oil × g × h_oil) + P_a
Where P_a is atmospheric pressure with a standard value of 1.01 × 10^(5) N/m²
g is gravitational acceleration = 9.81 m/s²
Thus;
P_abs = (1000 × 9.81 × 0.21) + (600 × 9.81 × 0.35) + (1.01 × 10^(5))
P_abs = 105120.2 N/m²
What is Energy in physics?
Answer:
Energy, in physics, the capacity for doing work. It may exist in potential, kinetic, thermal, electrical, chemical, nuclear, or other various forms. There are, moreover, heat and work—i.e., energy in the process of transfer from one body to another.
Explanation:
Hope this helps!
An airplane is flying at a speed of 200 m/s in level flight at an altitude of 800 m. A package is to be dropped from the airplane to land on a target on the ground. At what horizontal distance away from the target should the package be released so that it lands on the target
Answer:
The
Explanation:
The horizontal distance covered is known as the range expressed as;
R = U√2H/g
U is the speed = 200m/s
H is the max height = 800m
g is the gravity = 9.8m/s²
R = 200√2(800)/9.8
R = 200√1600/9.8
R = 200√163.27
R = 200(12.78)
R = 2555.54
Hence the package should be released at a distance of 2555.54m
What statement is TRUE about all the substances listed in the data table? A) All the substances conduct electricity. B) All the substances are strong electrolytes. All the substances have high dissociation constants. D) All the substances contain an equal amount of ions in solution. Eliminate
Answer:
A) all substance conduct electricity
Just some Naruto couples having a Boxing Match.
Who do you think will win?! Naruto and Hinata or Pain and Konan?!
Answer:
naruto and hinata
Explanation:
Which type of mass movement is likely to result in considerable property damage, but rarely causes loss of life? a. debris avalanche b. rock fall c. mudflow d. creep
Answer:
The correct answer is D. Creep.
Explanation:
Ground creep is a slow downward movement of a hill or mountain slope without the formation of demolition forms. The decisive factor for this is the continuous flow of movement of the soil.
The main driver of collapse is the movement of the surface layer particles during expansion in a direction perpendicular to the slope, followed by vertical collapse on contraction. The visible effect of the collapsing is the inclination of fences and poles, as well as trees that grow out of the ground towards the slope and have trunks curved vertically, in more extreme cases it may be cracks on the walls of buildings.
which is not a type of mechanical wave?
A film of soapy water on top of a plastic cutting board has a thickness of 255 nm. What wavelength and color is most strongly reflected if it is illuminated perpendicular to its surface?
Answer:
the reflected wavelength is lano = 4.55 10⁻⁷ m which corresponds to the blue color
Explanation:
This is a case of reflection interference, we must be careful
* There is a 180º phase change when light passes from the air to the soap film (n = 1,339), but there is no phase change when passing from the pomp to the plastic (n = 1.3)
* the wavelength within the film is modulated by the refractive index
λₙ = λ₀ / n
if we consider these relationships the condition for constructive interference is
2 t = (m + ½) λₙ
2t = (m + ½) λ₀ / n
λ₀ = 2t n / (m + ½)
we substitute the values
λ₀= 2 255 10⁻⁹ 1,339 / (m + ½)
λ₀ = 6.829 10⁻⁷ (m + ½)
let's calculate the wavelength for various interference orders
m = 0
λ₀ = 6.829 10⁻⁷/ ( 0 + ½ )
λ₀ = 13.6 10⁻⁷
it is not visible
m = 1
λ₀ = 6,829 10⁻⁷/ (1 + ½)
λ₀ = 4.55 10⁻⁷
color blue
m = 2
λ₀ = 6.829 10⁻⁷ / (2 + ½)
λ₀ = 2,7 10⁻⁷
it is not visible
therefore the reflected wavelength is lano = 4.55 10⁻⁷ m which corresponds to the blue color
How do we use energy transformation in our daily lives?
Answer:hat are some examples of energy transformation?
The Sun transforms nuclear energy into heat and light energy.
Our bodies convert chemical energy in our food into mechanical energy for us to move.
An electric fan transforms electrical energy into kinetic energy.
Explanation:
In a double-slit experiment, the second-order bright fringe is observed at an angle of 0.61°. If the slit separation is 0.11 mm, then what is the wavelength of the light?
Answer:
[tex]5.86\times 10^{-7}\ \text{m}[/tex]
Explanation:
d = Slit separation = 0.11 mm
[tex]\theta[/tex] = Angle = [tex]0.61^{\circ}[/tex]
m = Order = 2
[tex]\lambda[/tex] = Wavelength
We have the relation
[tex]d\sin\theta=m\lambda\\\Rightarrow \lambda=\dfrac{d\sin\theta}{m}\\\Rightarrow \lambda=\dfrac{0.11\times 10^{-3}\times \sin0.61^{\circ}}{2}\\\Rightarrow \lambda=5.86\times 10^{-7}\ \text{m}[/tex]
The wavelength of the light is [tex]5.86\times 10^{-7}\ \text{m}[/tex].
Jolie is on the weightlifting team at her school. She must lift as much weight as possible from the ground to a standing straight position. How much work will Jolie do if she uses a force of 5N to lift 150 pounds to a height of 1.5m? 0 2.3) O 6.5) 7.5) 0 3.3)
Answer:
=7.5J
Explanation:
Step one:
given data
the applied force F=5N
the distance = 1.5m
Step two:
Required
work done by Jolie
Now by definition, the work done is the applied times the distance which the force is applied
Wd= F*D
Wd= 5*1.5
Wd=7.5J
If she uses a force of 5N to lift 150 pounds to a height of 1.5m, the work done will be 7.5J
what is the force of gravitational attraction between a 92 kg student and a 550 g slice of pizza that are 25 cm apart
Answer:
[tex]F = 5.4*10^{-8}\ N[/tex]
Explanation:
Given
Represent the mass of the student with M and the mass of the slice of pizza with m
[tex]M = 92kg[/tex]
[tex]m = 550g[/tex]
[tex]d = 25cm[/tex]
Required
Determine the force of attraction
This is calculated as:
[tex]F = \frac{GMm}{d^2}[/tex]
Where G = gravitational constant
[tex]G = 6.67408 * 10^{-11}\ m^3 kg^{-1} s^{-2}[/tex]
Convert both mass to kilogram and distance to metre
[tex]m = 550g[/tex]
[tex]m = 550kg/1000[/tex]
[tex]m = 0.55kg[/tex]
[tex]d = 25cm[/tex]
[tex]d = 25m/100[/tex]
[tex]d = 0.25m[/tex]
Substitute these values in [tex]F = \frac{GMm}{d^2}[/tex]
[tex]F = \frac{6.67408 * 10^{-11} * 92 * 0.55}{0.25^2}[/tex]
[tex]F = \frac{6.67408 * 92 * 0.55* 10^{-11} }{0.25^2}[/tex]
[tex]F = \frac{337.708448* 10^{-11} }{0.0625}[/tex]
[tex]F = 5403.335168* 10^{-11}[/tex]
[tex]F = 5.403335168* 10^3*10^{-11}[/tex]
[tex]F = 5.403335168*10^{3-11}[/tex]
[tex]F = 5.403335168*10^{-8}[/tex]
[tex]F = 5.4*10^{-8}\ N[/tex]
match the variables to its definition
Answer:
See connections below
Explanation:
1 [tex]\Rightarrow[/tex] b
2 [tex]\Rightarrow[/tex] a
3 [tex]\Rightarrow[/tex] d
4 [tex]\Rightarrow[/tex] i
5 [tex]\Rightarrow[/tex] g
6 [tex]\Rightarrow[/tex] h
7 [tex]\Rightarrow[/tex] c
8 [tex]\Rightarrow[/tex] e
9 [tex]\Rightarrow[/tex] f
PLEASE HELP WITH A PHYSICS QUESTION!!!!
A bullet is dropped into a river from a very high bridge. At the same time, another bullet is fired from a gun straight down towards the water. If air resistance is negligible, how do the accelerations of the bullets compare just before they strike the water?
A. The acceleration is the same for both bullets.
B. The acceleration of the dropped bullet is greater.
C. The acceleration of the fired bullet is greater.
D. The comparison will depend on how high the bullets started.
Answer:
A. The acceleration is the same for both bullets.
Explanation:
The force of gravity is the attractive force applied by the earth on any object on its surface or neighborhood. And it is uniform under free fall at a definite location on the earth.
Since the the two bullets motion was at the same time and without air resistance, their acceleration would be the same before striking the surface of the water. This is because neglecting air resistance, all objects at the same height would fall with the same acceleration no matter their masses.
When does a magnet induce an electric current in a wire coil?
O A. When the wire is connected to the coil
O B. When the magnet is near the coil
O C. When the magnet is moving back and forth in the coil
D. When the magnet is very strong
Answer:
B I believe
Explanation:
I’ll give you a star if you answer this question. Which of the following is the best example of work being done
on an object?
If a car has a centripetal acceleration of 7m/s2 over a radius of 7m. How fast is it going
a. 7 m/s
b 1 m/s
с o m/s
d 49 m/s
Answer:
7 m/s (agrees with answer a in your list)
Explanation:
Recall that the centripetal acceleration is defined by the square of the tangential velocity divided by the radius of the rotational motion:
[tex]a_c=\frac{v_t^2}{R}[/tex]
then the tangential velocity is extracted from here as:
[tex]a_c=\frac{v_t^2}{R} \\v_t^2=a_c * R\\v_t=\sqrt{a_c * R}[/tex]
in our case, this becomes:
[tex]v_t=\sqrt{7*7} = 7 \,\,m/s[/tex]
An electromagnet needs a magnetic metal core. To produce a magnetic field,
what else is required?
A second metal core?
A solenoid with current or no current running through it? Or a permanent magnet?
Answer:solenoid with current running through it
Explanation:just took the test
A penny is dropped from rest from a building 100m tall. what kind of motion is this
A. centripetal
B. Free fall
C. Linear
D. projectile
Answer:
this is a projectile
Answer:
D. projectile
Explanation:
Since it's dropped from a rest that means that it's velocity at the beginning is 0.