When jumping straight down, you can be seriously injured if you land stiff-legged. One way to avoid injury is to bend your knees upon landing to reduce the force of the impact. A 63.5-kg man just before contact with the ground has a speed of 7.89 m/s. (a) In a stiff-legged landing he comes to a halt in 3.99 ms. Find the magnitude of the average net force that acts on him during this time. (b) When he bends his knees, he comes to a halt in 0.205 s. Find the magnitude of the average net force now. (c) During the landing, the force of the ground on the man points upward, while the force due to gravity points downward. The average net force acting on the man includes both of these forces. Taking into account the directions of the forces, find the magnitude of the force applied by the ground on the man in part (b).

Answers

Answer 1

Answer:

a)  F = 1.26 10⁵ N, b)  F = 2.44 10³ N, c)   F_net = 1.82 10³ N  directed vertically upwards

Explanation:

For this exercise we must use the relationship between momentum and momentum

         I = Δp

         F t = p_f -p₀

a) It asks to find the force

as the man stops the final velocity is zero

         F = 0 - p₀ / t

the speed is directed downwards which is why it is negative, therefore the result is positive

         F = m v₀ / t

         F = 63.5 7.89 / 3.99 10⁻³

         F = 1.26 10⁵ N

b) in this case flex the knees giving a time of t = 0.205 s

          F = 63.5 7.89 / 0.205

          F = 2.44 10³ N

c) The net force is

         F_net = Sum F

         F_net = F - W

         F_net = F - mg

let's calculate

         F_net = 2.44 10³ - 63.5 9.8

         F_net = 1.82 10³ N

since it is positive it is directed vertically upwards


Related Questions

A forward honzontal force of 50 N is applied to a crate. A second horizontal force o
180 N is applied to the crate in the opposite direction. Determine the magnitude and
direction of the resultant force acting on the crate​

Answers

Answer:

Explanation:

magnitude: 180-50=130N

Direction: in the direction same as the second horizontal force

Two sticky spheres are suspended from light ropes of length LL that are attached to the ceiling at a common point. Sphere AA has mass 2mm and is hanging at rest with its rope vertical. Sphere BB has mass mm and is held so that its rope makes an angle with the vertical that puts BB a vertical height HH above AA. Sphere BB is released from rest and swings down, collides with sphere AA, and sticks to it.
In terms of H,H, what is the maximum height above the original position of A reached by the combined spheres after their collision?

Answers

Answer:

  h’ = 1/9 h

Explanation:

This exercise must be solved in parts:

* Let's start by finding the speed of sphere B at the lowest point, let's use the concepts of conservation of energy

starting point. Higher

         Em₀ = U = m g h

final point. Lower, just before the crash

         Em_f = K = ½ m [tex]v_{b}^2[/tex]

energy is conserved

         Em₀ = Em_f

         m g h = ½ m v²

         v_b = [tex]\sqrt{2gh}[/tex]

* Now let's analyze the collision of the two spheres. We form a system formed by the two spheres, therefore the forces during the collision are internal and the moment is conserved

initial instant. Just before the crash

         p₀ = 2m 0 + m v_b

final instant. Right after the crash

         p_f = (2m + m) v

       

the moment is preserved

         p₀ = p_f

         m v_b = 3m v

         v = v_b / 3

         

          v = ⅓ [tex]\sqrt{2gh}[/tex]

* finally we analyze the movement after the crash. Let's use the conservation of energy to the system formed by the two spheres stuck together

Starting point. Lower

          Em₀ = K = ½ 3m v²

Final point. Higher

          Em_f = U = (3m) g h'

          Em₀ = Em_f

          ½ 3m v² = 3m g h’

           

we substitute

         h’=  [tex]\frac{v^2}{2g}[/tex]

         h’ =  [tex]\frac{1}{3^2} \ \frac{ 2gh}{2g}[/tex]

         h’ = 1/9 h

Constructive interference occurs when the crest of 2 waves meet. This can occur when 2 troughs meet as well. When this occurs, water waves look


A- the same (no change)


B- larger


C- invisible


D- smaller

Answers

Answer:

B; Larger

Explanation:

I took the K-12 quiz, and that was the correct answer. Hope this helped!

A5 N object at a height has gravitational potential energy of 30 J. What is the height of the object?​

Answers

30=5×h then divide both sides by 5 you will get h=6m

If a 5 N object at a height has a gravitational potential energy of 30 J , then the height of the object would be  6 meters.

What is mechanical energy?

Mechanical energy is the combination of all the energy in motion represented by total kinetic energy and the total potential energy stored energy in the system which is represented by total potential energy.

As given in the problem a 5 N object at a height has gravitational potential energy of 30 J, then we have to find the height of the object.

Similarly, the total gravitational  potential energy of the object,

PE = m × g × h

30  = 5 × h

h  = 30 / 5

h  = 6 meters

Thus, if a 5 N object at a height has a gravitational potential energy of 30 J, then the height of the object would be  6 meters.

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Which device increases or decreases voltage as electricity is transmitted from power plants to homes and businesses?

generator
power line
transformer
turbine

Answers

Answer:Transformer

Explanation:All the other devices generate their own electricity apart from power line and Transformer, power line just carries electricity. A transformer can be used to step up or step down voltages from a source.

Answer:

transformer!! :)

Explanation:

In the United States, household electric power is provided at a frequency of 60 HzHz, so electromagnetic radiation at that frequency is of particular interest. On the basis of the ICNIRP guidelines, what is the maximum intensity of an electromagnetic wave at this frequency to which the general public should be exposed

Answers

Answer:

the maximum intensity of an electromagnetic wave at the given frequency is 45 kW/m²

Explanation:

Given the data in the question;

To determine the maximum intensity of an electromagnetic wave, we use the formula;

[tex]I[/tex] = [tex]\frac{1}{2}[/tex]ε₀cE[tex]_{max[/tex]²

where ε₀ is permittivity of free space ( 8.85 × 10⁻¹² C²/N.m² )

c is the speed of light ( 3 × 10⁸ m/s )

E[tex]_{max[/tex] is the maximum magnitude of the electric field

first we calculate the maximum magnitude of the electric field ( E[tex]_{max[/tex]  )

E[tex]_{max[/tex] = 350/f kV/m

given that frequency of 60 Hz, we substitute

E[tex]_{max[/tex] = 350/60 kV/m

E[tex]_{max[/tex] = 5.83333 kV/m

E[tex]_{max[/tex] = 5.83333 kV/m × ( [tex]\frac{1000 V/m}{1 kV/m}[/tex] )

E[tex]_{max[/tex] = 5833.33 N/C

so we substitute all our values into the formula for  intensity of an electromagnetic wave;

[tex]I[/tex] = [tex]\frac{1}{2}[/tex]ε₀cE[tex]_{max[/tex]²

[tex]I[/tex] = [tex]\frac{1}{2}[/tex] × ( 8.85 × 10⁻¹² C²/N.m² ) × ( 3 × 10⁸ m/s ) × ( 5833.33 N/C )²

[tex]I[/tex] = 45 × 10³ W/m²

[tex]I[/tex] = 45 × 10³ W/m² × ( [tex]\frac{1 kW/m^2}{10^3W/m^2}[/tex] )

[tex]I[/tex] = 45 kW/m²

Therefore, the maximum intensity of an electromagnetic wave at the given frequency is 45 kW/m²

10. What patterns do you notice between the angles of incidence and the
angles of the reflected light rays?
1
EXPLORE/EXPLAIN Lesson 2 Reflection and Mir

Answers

Answer:

The law of reflection states that the angle of reflection equals the angle of incidence—θr = θi. The angles are measured relative to the perpendicular to the surface at the point where the ray strikes the surface.

Given three different locations on Earth's surface, where will the weight of a person be greatest?

Answers

Answer:

Explanation:

In order to answer this question, we simply have to refer to the laws of the equations of gravitational mechanics.

The equation given by Newton tells us that  

[tex]F = \frac{Gm_{1} m_{2} }{r^{2} }[/tex]

In the case where we compare a specific place where the Force of Gravity is greater or lesser, we focus on the term assigned to the Planet's Radius.

In the case of [tex]G, m_{1} ,m_{2}[/tex], we understand that they are constant.

We can easily notice that the more the Radius (Height seen from a viewer on the ground), the lower the force will be.

In other words, the smaller the radius in which the measurement is made with respect to the center of the earth, the greater the gravitational force.

In that order of ideas the smallest radio has South Pole, which is about 6356 km from the center of the Earth on the Equator line

A gas is stored in a sealed container of constant volume. The temperature of the gas increases.
This causes the pressure of the gas to increase
What happens to the gas molecules during this pressure increase?
A The average kinetic energy of the molecules increases.
B The average separation of the molecules decreases
The average separation of the molecules increases,
с
D
The volume of each molecule increases.

Answers

Answer:

If the gas volume is decreased, the container wall area decreases and the molecule-wall collision frequency increases, both of which increase the pressure exerted by the gas. Avogadro's law. At constant pressure and temperature, the frequency and force of molecule-wall collisions are constant.

Explanation:

As the temperature increases, the average kinetic energy increases as does the velocity of the gas particles hitting the walls of the container. The force exerted by the particles per unit of area on the container is the pressure, so as the temperature increases the pressure must also increase.

As the temperature of the gas increases, the particles gain kinetic energy and their speed increases. This means that the particles hit off the sides more often and with greater force. Both of these factors cause the pressure of the gas to increase.

What is temperature ?

Temperature is a measure of the degree of hotness of a body. The SI unit of temperature is kelvin (K).The instrument used to measure temperature is called a thermometer.

What is kinetic energy ?

Kinetic energy is a form of energy that an object or a particle has by reason of its motion. If work, which transfers energy, is done on an object by applying a net force, the object speeds up and thereby gains kinetic energy.

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The tundra is located _______.
a.
north of the equator
b.
south of the equator
c.
along the equator
d.
both north and south of the equator


Please select the best answer from the choices provided

A
B
C
D

Answers

Answer:

d: both north and south

Explanation:

If a force is applied, but the object does
not move, what can we say about the
amount of work that is done?
A. Some work is done.
B. No work is done.
C. The work equals the force.
D. A large amount of work is done.

Answers

Answer:

doesn't move, no work is done; if a force is applied and the object moves a distance d in a direction other than the direction of the force, less work is done than if the object moves a distance d in the direction of the applied.

Answer:

B. No work is done.

Explanation:

Work is only done when the object moves in the direction of the force.

What is the gravitational potential energy of a 3 kg ball that is 1 meter above the floor?

Answers

Answer:

PE=mgh

M= Mass (kg)

G= Gravitational field strength (N/kg)

H= Hight (m)

PE= Gravitational Potential Energy (J)

Explanation:

Gravitational Potential Energy is the energy stored in a object due to its position above the Earth's surface.

The potential energy of the ball is 29.4 joules

The parameters given are;

mass= 3 kg

height= 1 meter

g= 9.8 m/s²

P.E= mgh

= 3 × 9.8 × 1

= 29.4

Hence the potential energy is 29.4 joules

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what is the terminal velocity of blood

Answers

Answer:

25.1

Explanation:

what is the effect of cigarette smoke in your family​

Answers

the family gets second hand smoke?

Which of the following parallel plate diagrams would have the greatest electric fields between them?

Answers

The greatest electric field between them is Option B.

An electric field is the physical subject that surrounds electrically charged particles and exerts a force on all other charged debris inside the area, either attracting or repelling them. It also refers back to the bodily field of a machine of charged particles.

Reasoning:-

Electric field = Kq/r²

Since the distance is inversely proportional to the square root of the distance between them. therefore decreasing the distance electric field will be the greatest. Hence Option B.

The electrical field is defined mathematically as a vector discipline that can be related to each point in space, the force in step with unit charge exerted on a fine take a look at the price at rest at that factor. the electric field is generated by the electrical rate or through time-varying magnetic fields. electric fields provide us with the pushing force we need to set off the contemporary float.

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Which is a tool that use in medicine to view internal organs and pregnancy

Answers

an ultrasound? it’s commonly used to make pictures of internal organs and to check to see if someone is pregnant
An ultrasound scan uses high-frequency sound waves to make an image of a person's internal body structures.

can someone pls tell me what a force diagram is​

Answers

A diagram showing the forces acting on the object. The object is represented by a dot with forces are drawn as arrows pointing away from the dot. Sometimes called force diagrams.

Two copper rods are rubbed together will they become charged

Answers

Answer:

Explanation:When insulating materials rub against each other, they may become electrically charged . Electrons , which are negatively charged, may be 'rubbed off' one material and on to the other. The material that gains electrons becomes negatively charged.

Can you please help me with this worksheet I will give BRAINLISET to whoever answers first?

Answers

I can not see nun it’s black

2. Which process is used by plants to cycle water from the ground, through the roots, and out the leaves as water vapor?
sublimation
O perspiration
O transpiration
O runoff

Answers

Answer:

The answer is transpiration

Perspiration is the answer

they enjoy being alone for quit small time​

Answers

Yeah and? What’s the question

2. What will be the extension of this spring if the load is a) 4N and b) 75 g?

Answers

Answer:

6

Explanation:

just add

In 1994, Leroy Burrell of the United States set what was then a new world record for the men’s 100 m run. He ran the 1.00  102 m distance in 9.5 s. Assuming that he ran with a constant speed equal to his average speed, and his kinetic energy was 3.40  103 J, what was Burrell’s mass?

Answers

Answer:

61.33 Kg

Explanation:

From the question given above, the following data were obtained:

Distance = 1×10² m

Time = 9.5 s

Kinetic energy (KE) = 3.40×10³ J

Mass (m) =?

Next, we shall determine the velocity Leroy Burrell. This can be obtained as follow:

Distance = 1×10² m

Time = 9.5 s

Velocity =?

Velocity = Distance / time

Velocity = 1×10² / 9.5

Velocity = 10.53 m/s

Finally, we shall determine the mass of Leroy Burrell. This can be obtained as follow:

Kinetic energy (KE) = 3.40×10³ J

Velocity (v) = 10.53 m/s

Mass (m) =?

KE = ½mv²

3.40×10³ = ½ × m × 10.53²

3.40×10³ = ½ × m × 110.8809

3.40×10³ = m × 55.44045

Divide both side by 55.44045

m = 3.40×10³ / 55.44045

m = 61.33 Kg

Thus, the mass of Leroy Burrell is 61.33 Kg

When a 2kg metal is exposed to 2MJ of
heat it dissolves into liquid at 500K
Calculate the latent heat of fusion for
the metal. Betty went in to get you metal is exposed to to megajoules of heat ​

Answers

Answer:

1×10⁶ J/Kg

Explanation:

From the question given above, the following data were obtained:

Mass (m) of metal = 2 Kg

Heat (Q) = 2 MJ

Latent heat of Fusion (Hf) =?

Next, we shall convert 2 MJ to J. This can be obtained as follow:

1 MJ = 1×10⁶ J

Therefore,

2 MJ = 2 MJ × 1×10⁶ J / 1 MJ

2 MJ = 2×10⁶ J

Finally, we shall determine the latent heat of fusion. This can be obtained as follow:

Mass (m) of metal = 2 Kg

Heat (Q) = 2×10⁶ J

Latent heat of Fusion (Hf) =?

Q = m•Hf

2×10⁶ = 2 × Hf

Divide both side by 2

Hf = 2×10⁶ / 2

Hf = 1×10⁶ J/Kg

Thus, the latent heat of fusion for the metal is 1×10⁶ J/Kg

miniature spring-loaded, radio-controlled gun is mounted on an air puck. The gun's bullet has a mass of 5.00 g, and the gun and puck have a combined mass of 120 g. With the system initially at rest, the radio controlled trigger releases the bullet causing the puck and empty gun to move with a speed of 0.500 m/s. What is the bullet's speed

Answers

Answer:

12 m/s

Explanation:

From the question,

Applying the law of conservation of momentum,

total momentum before collision = Total momentum after collision

mu+Mu' = mv+Mv'........................... Equation 1

Where m = mass of the bullet, u = initial velocity of the bullet, M = combined mass of the gun and the puck, u' = initial velocity of the gun and the puck, v = final velocity of the bullet, v' = final velocity of the gun and the puck

make v the subeject of the equation

v = [(mu+Mu')-Mv']/m................. Equation 2

Given: m = 5.00 g = 0.005  kg, M = 120 g = 0.12 kg, u = u' = 0 m/s (at rest), v' = 0.5 m/s

Substitute these values into equation 2

v = [0-(0.12×0.5)]/0.005

v = -0.06/0.005

v = -12 m/s

The negative sign  can be ignored since we are looking for the speed, which has only magnitude.

Hence the speed of the bullet is 12 m/s

PLEASE HELP ASAP!!!
A car is sitting on a hill which is 25 m higher than ground level. What is the mass of the car if it contains 360,800 J of potential energy?

Answers

Answer:

14,432 g

Explanation:

PE=mh

360,800 J = (m)(25)

[tex]\frac{360,800 J}{25 m}[/tex] = m

14,432 g = m

Rolled cookies are cut into fancy shapes.

True
False

Answers

Answer:

false

Explanation:

the answer is false

Answer:

true

Explanation:

cause why not, try new things init

What order shows increasing frequency for gamma
rays, microwaves, visible light, and X-rays?
A. gamma rays, X-rays, visible light, microwaves
B. microwaves, visible light, X-rays, gamma rays
C. visible light, gamma rays, microwaves, X-rays
D. X-rays, microwaves, gamma rays, visible light

Answers

Answer:

The answer is B: microwaves, visible light, X-rays, gamma rays

Explanation:

I had the same question and I got option B as the correct answer.

The waves arranged in their order of increasing frequency will be

Microwaves,Visible light, X-rays and Gamma rays.

What order shows the increasing frequency for gamma rays, microwaves, visible light, and X-rays?

Generally, frequency is the numeral of occurrences of a repeating event per unit of duration.

Therefore, gamma rays, microwaves, visible light, and X-rays  will be arranged in their order of  increasing frequency

In conclusion, The order is given as folllows

microwaves, Visible light, X-rays, and Gamma rays.

Option B is correct

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We observe that a moving charged particle experiences no magnetic force. From this we can definitely conclude that: (A) No magnetic field exists in that region of space. (B) The particle must be moving parallel to the magnetic field. (C) Either no magnetic field exists or the particle is moving parallel to B. (D) Either no magnetic field exists or the particle is moving vertical (perpendicular) to B.

Answers

Answer:

(C) Either no magnetic field exists or the particle is moving parallel to B.

Explanation:

The moving charged particle tends to show no magnetic forces. Due to its moving in the same direction and will be parallel to the field. As when the magnetic fed and charged particle velocity is parallel then there will be no force. As the magnetic field are made by the generation of the current with the field line concentric to the current-carrying wire.

An Atwood's machine consists of two masses, m1 and m2, connected by a string that passes over a pulley. If the pulley is a disk of radius R and mass M , find the acceleration of the masses. Express your answer in terms of the variables m1, m2, R, M, and appropriate constants.

Answers

Answer:

Explanation:

Suppose m₂ is greater than m₁ and it is going down . m₁ will be going up.

Let tension in string be T₁ and T₂  . Let common acceleration of system be a

For motion of m₁

T₁-m₁g = m₁a ----- (1)

For motion of m₂

m₂g- T₂ = m₂a ------- (2)

For motion of pulley

(T₂-T₁ )R represents net torque

(T₂-T₁ )R = I x α where I is moment of inertia of disc and α is angular acceleration of disc

(T₂-T₁ )R = 1/2 M R² x a / R

(T₂-T₁ ) = M a /2

Adding (1) and (2)

(m₂-m₁)g = (m₂+m₁)a + (T₂-T₁ )

(m₂-m₁)g = (m₂+m₁)a + Ma/2

(m₂-m₁)g = (m₂+m₁+ 0.5M)a

a = (m₂-m₁)g / ( (m₂+m₁+ 0.5M)

The acceleration of the masses is [tex]\dfrac{g(m_2+m_1)}{(m_2-m_1-0.5M)}[/tex].

Given to us

Masses = m₁, m₂

The radius of the pulley = R

Mass of the pulley = M

Assumption

Let the mass m₁ > m₂. therefore, the mass m₁ is going down due to its weight while m₂ is going up.Assuming the tension in the string be T₁ and T₂, respectively.Also, the common acceleration in the system is a.

Tensions in strings

We know the acceleration due to gravity is denoted by g,

Tension in string 1, T₁

[tex]T_1 = m_1(a+g)[/tex]......... equation 1

Tension in string 2, T₂

[tex]T_2 = m_2(a-g)[/tex]......... equation 2

Inertia and acceleration of the pulley

The inertia of the pulley,  [tex]I = \dfrac{1}{2}MR^2[/tex]

Acceleration of the pulley, [tex]a = {\alpha }\times {R}[/tex]

Torque in the pulley

[tex](T_2-T_1)R = I \times \alpha \\\\[/tex]

Substitute the values we get,

[tex][m_2(a-g)-m_1(a+g)]R = \dfrac{1}{2} MR^2 \times \dfrac{a}{R}\\\\[/tex]

[tex][m_2a-m_2g-m_1a-m_1g]R= \dfrac{1}{2} MR \times a[/tex]

[tex]m_2a-m_1a-m_2g-m_1g= \dfrac{1}{2} M \times a[/tex]

[tex]a(m_2-m_1)-g(m_2+m_1)= 0.5M \times a[/tex]

[tex]a(m_2-m_1)-0.5Ma=g(m_2+m_1)\\\\a(m_2-m_1-0.5M) = g(m_2+m_1)\\\\a = \dfrac{g(m_2+m_1)}{(m_2-m_1-0.5M)}[/tex]

Hence, the acceleration of the masses is [tex]\dfrac{g(m_2+m_1)}{(m_2-m_1-0.5M)}[/tex].

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