A 70 kg child escapes from a burning building by walking off a roof 30 m above a catching net. Assuming that resistance is a constant 90 N on the child during their fall, calculate the person's velocity just before hitting the net.
Answers
Newton's second law and kinematics allow to find the result for the velocity at the point of reaching the child's net is:
v = 23.7 m / s
Newton's second law states that the net force is proportional to the mass and acceleration of the body.
∑ F = m a
Where F is the force, m the mass and the acceleration of the body.
In the attachment we can see a free body diagram of the system, where the positive direction is up.
F -W = m a
Weight is
W = m g
[tex]a = \frac{F}{m} - g[/tex]
Let's calculate
[tex]a= \frac{30}{70} - 9.8[/tex]
a = -9.37 m / s²
Negative indicates downward direction.
Kinematics studies the movement of the body, let's look for speed.
v² = v₀² - 2 a (y-y₀)
Where v is the speed, v₀ is the initial speed, a tha acceleration ang (y-y₀) is the eight.
As the child is released, his initial velocity is zero, upon reaching the floor his height is zero and his initial height is I = 30 m.
[tex]v= \sqrt{2 a y_o}[/tex]
Let's calculate
v = [tex]\sqrt{2 \ 9.37 \ 30}[/tex]
v = 23.7 m / s
In conclusion using Newton's second law and kinematics we can find the velocity at the point where the child reaches the net is:
v = 23.7 m / s
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The velocity of the child before hitting the ground is 22.596 m/s.
The given parameters;
mass of the child, m = 70 kgheight of the roof, h = 30 mair resistance on the child, F = 90 NThe weight of the child acting downwards is calculated as follows;
W = mg
W = 70 x 9.8
W = 686 N
The net force on the child is calculated as follows;
∑Fₙ = 686 N - 90 N
∑Fₙ = 596 N
The acceleration of the child is calculated as follows;
F = ma
[tex]a = \frac{F}{m} \\\\a = \frac{596}{70} \\\\a = 8.51 \ m/s^2[/tex]
The velocity of the child before hitting the ground is calculated as;
v² = u² + 2as
v² = 0 + (2 x 8.51 x 30)
v² = 510.6
v = √510.6
v = 22.596 m/s
Thus, the velocity of the child before hitting the ground is 22.596 m/s.
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Related Questions
pls need an answer asap
Answers
c] Electrons
Electron gets transferred
A 1.11 kg ball sits at rest on a table 1.72 m above the ground. What is the potential energy of the ball?
Answers
Answer:
18.71 joules
Explanation:
The formula to solve for potential energy is PE = mgh
where m = mass, g = force of gravity, and h = height.
m = 1.11 kg
g = 9.8 m/s^2
h = 1.72 meters
PE = (1.11)(9.8)(1.72)
PE = 18.71016
Therefore, the potential energy of the ball is 18.71 joules.
Answer:
The formula to solve for potential energy is PE = mgh
where m = mass, g = force of gravity, and h = height.
m = 1.11 kg
g = 9.8 m/s^2
h = 1.72 meters
PE = (1.11)(9.8)(1.72)
PE = 18.71016
Therefore, the potential energy of the ball is 18.71 joules.
calculate the density of a 50 ml solution that is 5% water and 95% ethanol. show your calculation.
Answers
The density of the solution from the given compositions of water and ethanol is 799.55 kg/m³.
The given parameters;
Volume of the solution, v = 50 mlComposition of water, 5%Composition of ethanol, 95%Density of water, = 1000 kg/m³Density of ethanol, = 789 kg/m³The density of the solution from the given compositions of water and ethanol is obtained by finding the respective amount of water and ethanol composition is the solution.
The density of the solution is calculated as follows;
[tex]\rho = \frac{5(1000 \ kg/m^3) + 95(789 \ kg/m^3)}{100} \\\\\rho = 799.55 \ kg/m^3[/tex]
Thus, the density of the solution from the given compositions of water and ethanol is 799.55 kg/m³.
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The answer is 799.55 kg/m3.
Which statement about the universality of gravity is untrue?
a
The gravitational force between two objects depends only on their masses.
b
The gravitational force between two objects increases if the mass of one object increases.
c
The gravitational force between two objects increases if the distance between the objects decreases.
d
Any two objects that have mass also have a force of gravity acting between them, no
Answers
Answer:
Explanation:
See attachment.
a NO - it depends on distance between the masses, also.
The gravitational force between two objects depends only on their masses.
b YES - see attachment
The gravitational force between two objects increases if the mass of one object increases.
c. No - it decrease
The gravitational force between two objects increases if the distance between the objects decreases.
d. It appears the answer is incomplete (stops at . . ., no . . ). Otherwise I say YES.
Any two objects that have mass also have a force of gravity acting between them, no
Biểu diễn những lực sau đây:
a. Trọng lực của một vật 300N ( tỉ xích 0.5cm ứng với 50N )
b. Lực kéo tác dụng vào điểm A của một vật có độ lớn 1500N theo phương nằm ngang, chiều từ trái sang phải ( 1cm ứng với 500N )
Answers
Answer:
Explanation: HIII
Which statement best describes the air in Earth's atmosphere?
- a pure substance made of one kind of gas
- a solution of gases that are physically mixed
- a compound made of two or more kinds of gases
- a mixture of two gases that are chemically combined
Answers
Explanation:
Please Tell me About this question if you know que is transformer is used in rectifier to step up or step down voltage?
What are solar flares, and how do they impact Earth?
Answers
Answer:
Explanation:
Flares occur in active regions around sunspots, where intense magnetic fields penetrate the photosphere to link the corona to the solar interior. ... X-rays and UV radiation emitted by solar flares can affect Earth's ionosphere and disrupt long-range radio communications.
If the mass of an object is 35grams and it takes 7 cm3 of space ,calculate the density
Answers
imagine a shopping cart of mass m, moving at a velocity of v to the right, running into a second shopping cart, of mass 3m, which is at rest.
Answers
The impulse is the product of mass and velocity. Hence, the impulse delivered by the second shopping cart is 3mv/2
Given the Parameters :
Mass of cart 1 = m Initial Velocity and direction = v toward the right Final velocity = v/2 towards the left Mass of cart 2 = 3m Velocity = 0 m/s (At rest)Impulse delivered by the second cart on the first :
Impulse = Mass × velocity
Impulse = Mass of cart 2 × final velocity of cart 1
Impulse = 3m × v/2 = 3mv/2 Ns (towards the left)
Therefore ; the impulse delivered by the second shopping cart is 3mv/2 to the left.
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the perimeter of a rectangle is 28 inches if the width of the rectangle is 7 inches what is the length
Answers
it needs to b 20 characters so im adding all this extra stuff, its 4 tho
can i get help with this worksheet
Answers
Answer:
hi uv f hmm k in vyvj
Explanation:
hujjkiv ghujihtnkbggvhbbbnnjnj
напряженность поля в некоторой точке 0,8 кН/кл определите величину силы,с которой поле будет в этой точке действовать на заряд 2,5мкКл
Answers
Answer:
напряженность поля в некоторой точке 0,8 кН/кл определите величину силы,с которой поле будет в этой точке действовать на заряд 2,5мкКл 00
why are protons and electrons attracted to each other
Answers
Answer:
electrons have a negative charge, while protons have a positive charge
Explanation:
In science "opposites attract"
How much time would it take for the sound of Thunder to travel 2000 meters if sound travels a speed of 330 meters per sec.
Answers
Answer:
6.06 seconds i believe (rounded)
i just divided.
Which of the following keeps the planets in their orbits in the solar system?
A. Friction
B. Gravity
C. Magnetism
D. Pressure
Answers
B is the correct answer
What is the mass of an object if it accelerates at 3 m/s? and has a force of
1 N?
Answers
Answer:
1 / 3 or 0.33
that is if you meant that the object accelerates at 3 m / s² not 3 m / s
for the unit of acceleration is m / s²
Explanation:
m = ?
a = 3
f = 1N
where;
m = mass ( kg )
a = acceleration ( m / s² )
f = force ( N )
from all the parameters we are given, we can use Newton's second law of motion to solve it
that is;
a = f / m
to make m the subject of the formula, we have to cross multiply to give us;
m( a ) = f
divide through by a to give us;
m ( a ) / a = f / a
therefore,
m = f / a
so, we substitute our values to give us;
m = 1 / 3
therefore. m = 1 / 3 or 0. 33
hope this helps
thank you!!!!
What is an object's acceleration that takes 550.0 meters to go from 6.0 m/s to
85.0 m/s?
Answers
from,
v² = u² + 2as
where s = distance
a = (v² - u²) /2s
a = (85² - 6²) /2*550
a = 6.53m/s²
how are wavelength, frequency, and energy related for photons of light?
Answers
The wavelength and the frequency of the light are inversely proportional to each other, the multiplication of the wavelength and the frequency of the light is equal to the speed of the light.
What is Wavelength?It can be understood in terms of the distance between any two similar successive points across any wave for example wavelength can be calculated by measuring the distance between any two successive crests.
C = λν
As given in the problem we have to find out how are wavelength, frequency, and energy-related to photons of light,
The relationship between the wavelength and the frequency of light is inverse, and the product of the wavelength and the frequency equals the speed of light.
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1. Which of the following does not play a role in convection in the mantle?
A. gravity
B. temperature
C. density
D. magnetism
Answers
Answer:
Magnetism
Explanation:
Calculate the following:
D = 35 m
T = 17 sec
V = ?
Answers
Hope it helps :)
when the weight of the object increase block what is the force of friction applied? Explanation?
Answers
Answer:
There is absolutely No relationship between the weight of an object (which is constant) and the frictional force. If a block is sliding on a surface, that surface will be exerting a force on the block. That force can be resolved into a component parallel to the surface (which we call the frictional component), and a component perpendicular to the surface (called the normal component). For many situations, we find experimentally that the frictional component is approximately proportional to the normal component. The frictional component divided by the normal component is defined to be a quantity called the coefficient of kinetic or sliding friction. The coefficient of kinetic friction obviously depends on the nature of the surfaces involved. The normal component on an object can be decreased if you pull in the direction of the normal component (the weight does not change). However pulling this way on the object not only decreases the normal component, but it also decreases the frictional component since they are proportional. This is why it is easier to slide something if you pull up on it while you push it. If you push down, the normal and frictional components increase so it is harder to slide the object. The weight of an object is the downward force exerted by Earth’s gravity on that object, and it does not change no matter how you push or pull on the object.
When a 10V battery is connected to a resistor, 2A of current flows in the resistor.What is the resistors value? Formulas: V=IR, I=V/R, R=V/INote no need to write the unit in your answer.help im dying
Answers
Answer:
V = 10
I = 2
R = ?
from,
R = V/I
R = 10/2 = 5 ohms.
P.S; don't die. :))
Students are given the following information about a 2.0 kg, motorized toy boat on water. what net force is exerted on the boat from 4S to 8S?
Answers
The motorized toy boat experiences a net force of 0 N between 4 s and 8 s.
The motorized toy boat moves at 8 m/s (u) at 4 s and at 8 m/s (v) at 8 s. We can calculate the acceleration (a) in that period using the following kinematic expression.
[tex]a = \frac{v-u}{\Delta t} = \frac{8m/s-8m/s}{8s-4s} = 0 m/s^{2}[/tex]
The object with a mass (m) of 2.0 kg experiences an acceleration of 0 m/s². We can calculate the net force (F) in that period using Newton's second law of motion.
[tex]F = m \times a = 2.0 kg \times 0 m/s^{2} = 0 N[/tex]
The motorized toy boat experiences a net force of 0 N between 4 s and 8 s.
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Let’s say someone drops to Waterman off a skyscraper. The second watermelon is released 1s after The first watermelon. Will the vertical distance between the watermelons always be the same
Answers
Answer:
Yes
Explanation:
They will reach the ground right after each other.
4. What is the purpose of the corneal reflex?
Answers
help2$2$28/?$3!32$?3)3
Answers
What is the density of the football in g/cm
Answers
Answer: see below.
Explanation:
Your question is lacking the necessary parameters, so I will assume the values to enable me to solve it:
Mass of football = 20 grams
Volume of football = 100[tex]cm^{3}[/tex]
To find the density of the football;
Density is simply mass per unit volume of an object such as a football.
Mathematically, the density of an object is given by the formula;
Density=[tex]\frac{Mass}{Volume}[/tex]
Substituting the assumed values into the above formula;
Density=[tex]\frac{20}{100}[/tex]
Density= 0.2g/[tex]cm^{3}[/tex]
Therefore, the density of the football is 0.2g/[tex]cm^{3}[/tex] .
For you: You can substitute the appropriate parameters into the formula to get the exact density of the ball.
Fig. 2.1 is a head-on view of an airliner flying at constant speed in a circular horizontal path.
The centre of the circle is to the left of the diagram.
The weight of the airliner is 1.20 x 10^6 N and there is an aerodynamic lift force of
1.39 x 10^6N acting to the left by drawing a scale vector
Ps: ^ to the power of
Answers
[tex]1.39[/tex] × [tex]10^{6} N[/tex] acting [tex]30^{o}[/tex] to the left of the vertical.
Constant speed:We refer to an object as traveling at a constant speed when its speed is constant and neither rises nor falls, at a continuous rate.Lift:A force is applied to an object by a fluid flowing around it. The part of this force that is perpendicular to the direction of the incoming flow is called lift. In contrast, the drag force, or portion of the force parallel to the flow direction, is the opposite. Lift typically acts upward to counteract the pull of gravity, but it can also act at an angle to the flow in any direction.The force is referred to as an aerodynamic force if the fluid is air.It is known as a hydrodynamic force in water or any other liquid.Solution -The weight of the airliner is [tex]1.20[/tex] × [tex]10^{6} N[/tex] and there is an aerodynamic lift force of [tex]1.39[/tex] × [tex]10^{6} N[/tex] acting [tex]30^{o}[/tex] to the left of the vertical.
Therefore, the airliner follows this circular path while maintaining a steady speed.
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Explain why a clothes iron with a metal base must be connected to the mains by a three-core cable.
Answers
The earth connection is because the earth connection(third cable) helps to prevent the casing from turning into a live wire.
What are the three cables?It is normal to find that the cable that is used in the pressing iron has three wires that connect to live, neutral and earth. The earth connection is very important in the pressing iron.
The reason why we ought to have the earth connection is because the earth connection helps to prevent the casing from turning into a live wire.
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¿Por qué crees que es importante desarrollar actividad física habitualmente, así como practicar hábitos de higiene saludable?
Answers
La actividad física posee muchos beneficios para la salud. Algunos de estos beneficios son la reducción en el riesgo de padecer enfermedades, control del peso, fortalecimiento de huesos y músculos, etc.
La actividad física regular previene la aparición de enfermedades cardiovasculares al evitar la acumulación de colesterol en las arterias que transportan sangre a diferentes áreas del organismo.
La actividad física consume calorías, especialmente aquellas provenientes de los lípidos (grasas), con lo cual permite controlar el peso y reducir el riesgo de obesidad.
La actividad física también ayuda al fortalecimiento de los tejido oseo, con lo cual previniendo enfermedades relacionadas tales como la osteoporosis.
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