Lightning occurs when there is a flow of electric charge (principally electrons) between the ground and a thundercloud. The maximum rate of charge flow in a lightning bolt is about 20,000 C/s this lasts for 100 μs or less.1. How much charge flows between the ground and the cloud in this time? (Q= ? C)2. How many electrons flow during this time? (n_e = ?)

Answers

Answer 1

Answer:

a

 The  charge is  [tex]Q =  2.0*10^8 \  C[/tex]

b

The number of electrons  [tex]N  =  1.25 *10^{27} \  electrons[/tex]

Explanation:

From the question we are told that

    The  maximum rate of charge flow is  [tex]\frac{dq}{dt} = I =  20000 \  C/s[/tex]

Here  I means current

    The time interval is [tex]t=100 \mu s  = 100*10^{-6}[/tex]

Generally the amount of charge is mathematically represented as

        [tex]Q =  \frac{I}{t}[/tex]

=>      [tex]Q =  \frac{20000}{ 100*10^{-6}}[/tex]

=>    [tex]Q =  2.0*10^8 \  C[/tex]

The number of electrons that flow during that time is evaluated as

    [tex]N  =  \frac{Q}{e}[/tex]

Here e is the charge on a single electron with value [tex]e=  1.60*10^{-19} \  C[/tex]

So

         [tex]N  =  \frac{2.0*10^8}{ 1.60*10^{-19}}[/tex]

         [tex]N  =  1.25 *10^{27} \  electrons[/tex]


Related Questions

Which of these terms is defined as the ability to cause motion or create change? A. efficiency B. energy C. force D. sound

Answers

The term that defines the ability to cause motion or create change is called force. Details about force can be found below.

What is force?

Force is the physical quantity that denotes ability to push, pull, twist or accelerate a body and which has a direction.

Force is measured in Newtons and can be calculated by multiplying the mass of the body by its acceleration.

Therefore, it can be said that the term that defines the ability to cause motion or create change is called force.

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A ball of mass m moving with speed V collides with another ball of mass 2m (e= 1/2) in a horizontal smooth fixed circular tube of radius R (R is sufficiently large R>>>d). The time after which next collision will take place is:________

Answers

Answer:

[tex]$ \frac{4\pi R}{V}$[/tex]

Explanation:

Given :

Mass of ball 1 = m

Mass of ball 2 = 2m

Since, R>>>d, the collision is head on.

Therefore, we get

[tex]$ \frac{v_1 -v_2}{V}=\frac{1}{2}$[/tex]

[tex]$ \therefore \frac{\text{velocity of seperation}}{\text{velocity of approach}}= v_1-v_2 = \frac{V}{2}$[/tex]

Relative velocity is given by V/2. So, we get the time when the masses will again collide as

[tex]$ t = \frac{2\pi R}{\frac{V}{2}}=\frac{4\pi R}{V} $[/tex]

A runner jumps off the ground at a speed of 16m/s. At what angle did he jump from the ground if he landed 8m away?​

Answers

Answer:lol I don’t know good qeustion

Explanation:

A Lotus will travel 275 meters in 4.71 seconds. What is this car's average speed?

Answers

390 Because it is what it is

A paper airplane is thrown horizontally with a velocity of 20 mph. The plane is in the air for 7.63 s before coming to a standstill on the ground. What is the acceleration of the plane?

Answers

Answer:

-1.17 m/s²

Explanation:

Given:

v₀ = 20 mph = 8.94 m/s

v = 0 m/s

t = 7.63 s

Find: a

v = at + v₀

0 m/s = a (7.63 s) + 8.94 m/s

a = -1.17 m/s²

The acceleration of the plane will be:

"-1.17 m/s²".

Acceleration and Velocity

According to the question,

Velocity, v₀ = 20 mph or,

                   = 8.94 m/s

and,

                v = 0 m/s

Time, t = 7.63 s

We know the relation,

→ v = at + v₀

By substituting the values,

  0 = a × 7.63 + 8.94

7.63a = - 8.94

      a = -[tex]\frac{8.94}{7.63}[/tex]

         = - 1.17 m/s²  

Thus the response above is correct.

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An electron with a speed of 0.95c is emitted by a supernova, where cc is the speed of light. What is the magnitude of the momentum of this electron?

Answers

Answer:

2.59×10¯²² Kgm/s

Explanation:

Data obtained from the question include:

Velocity of electron = 0.95c

Momentum =?

Next, we shall determine the velocity of the electron. This can be obtained as follow:

Velocity of electron = 0.95c

Velocity of Light (c) = 3×10⁸ m/s

Velocity of electron = 0.95c

Velocity of electron = 0.95 × 3×10⁸

Velocity of electron = 2.85×10⁸ m/s

Finally, we shall determine the mometum of the electron.

Momentum is simply defined as the product of mass and velocity. Mathematically, it is expressed as:

Momentum = mass x Velocity

Thus, with the above formula, we calculate the momentum of the electron as follow:

Mass of electron = 9.1×10¯³¹ Kg

Velocity of electron = 2.85×10⁸ m/s

Momentum of electron =?

Momentum = mass x Velocity

Momentum = 9.1×10¯³¹ × 2.85×10⁸

Momentum = 2.59×10¯²² Kgm/s

Therefore, the momentum of the electron is 2.59×10¯²² Kgm/s

Explain why a Merry-Go-Round and a Ferris Wheel have a constant acceleration when they are moving?

Answers

Answer:

merry go round and Ferris wheel have a constant acceleration due to the change in direction at every point.

Answer:

A merry-go-round is accelerating. Acceleration is a change in speed, direction, or both. Even though the speed of the merry-go-round does not change, its direction constantly changes as it spins.

Explanation:

A certain common-emitter amplifier has a voltage gain of 100. If the emitter bypass capacitor is removed:___________.
a. The circuit will become unstable b. The voltage gain will decrease
c. The voltage gain will increase d. The circuit will become stable

Answers

Answer:

b the voltage gain will decrease

Explanation:

Q=CV

it is easier to swim in Ocean than in a water​

Answers

Answer:

Explanation:

Ocean contains salty water which causes the object to float rather than sinking, So yes it's easy to swim in ocean than water without salt.

which water molecules have the greatest kinetic energy

Answers

The higher the temperature the substance is, the more energy in it because the particles are moving a lot more around in it. So therefore, steam which has the highest temperature, has the greatest kinetic energy.

A commuter backs her car out of her garage with an acceleration of 1.40 m/s2.A) How long does it take her to reach a speed of 2.00 m/s?B) If she then breaks to a stop in 0.800 s, what is her deceleration?

Answers

Answer:

(A) 1.43secs

(B) -2.50m/s^2

Explanation:

A commuter backs her car out of her garage with an acceleration of 1.40m/s^2

(A) When the speed is 2.00m/s then, the time can be calculated as follows

t= Vf-Vo/a

The values given are a= 1.40m/s^2 , Vf= 2.00m/s, Vo= 0

= 2.00-0/1.40

= 2.00/1.40

= 1.43secs

(B) The deceleration when the time is 0.800secs can be calculated as follows

a= Vf-Vo/t

= 0-2.00/0.800

= -2.00/0.800

= -2.50m/s^2

A satellite dish has the shape of a parabola when viewed from the side. The dish is inches wide and inches deep. How far is the receiver from the bottom of the dish if the receiver is placed at the focus

Answers

Complete question is;

A satellite dish has the shape of a parabola when viewed from the side. The dish is 60 inches wide and 45 inches deep. How far is the receiver from the bottom of the dish if the receiver is placed at the focus?

Answer:

the receiver should be put 40 inches from the bottom of the dish on the concave side of the dish

Explanation:

The base of the dish would simply be the vertex of parabola.

Since we want to find how far the receiver is from the bottom, the place where we'll place the receiver is simply the focus of the parabola.

Now, for example, if this is a parabola that opens upward and has it's vertex at the origin, then half of the diameter at a height of 45 inches gives the two points (60, 22.5) and (-60, 22.5)

Standard form equation of parabola with vertex at origin and pointing upwards is given by;

x² = 4ay

Plugging in the values of x and y gives;

60² = 4a(22.5)

3600/90 = a

a = 40 inches

Thus, the receiver should be put 40 inches from the vertex on the concave side of the dish

A -5.40nC point charge is on the x axis at x = 1.25m . A second point charge Q is on the x axis at -0.625m.
A) What must be the charge Q for the resultant electric field at the origin to be 50.0N/C in the +x direction?
B) What must be the charge Q for the resultant electric field at the origin to be 50.0N/C in the -x direction?

Answers

Answe

a)  Q = 0.820 10⁻⁹ C ,   b)  Q = -3.52 10⁻⁹ C

Explanation:

The electric field is given by the formula

         E = k q / r²

where E is a vector quantity, so it must be added as a vector

          E_total = E₁ + E₂

let's look for the two electric fields

           E₁ = k q₁ / r₁²

           E₁ = 9 10⁹  5.4 10⁻⁹ / 1.25²

           E₁ = 31.10 N / C

           E2 = k Q / r₂²

           E2 = 9 10⁹ Q / 0.625²

           E2 = 23.04 10⁹ Q N / C           (1)

now we can solve the two cases presented

a) The total field is

            E_total = 50.0 N / C towards + x

since the test charge is positive the electric field E1 points to the right in the direction of the + x axis, so the equation is

            E_total = E1 + E₂

             E₂ = E_toal - E₁

             E₂ = 50.0 -31.10

             E2 = 18.9 N /C

With the value of the electric field we can calculate the charge (Q) using equation 1

             E₂ = 23.04 10⁹ Q

              Q = E₂ / 23.04 10⁹

              Q = 18.9 / 23.04 10⁹

              Q = 0.820 10⁻⁹ C

the charge on Q is positive

b) E_total = -50.0 N / C

              E_total = E₁ + E₂

              E₂ = E_total - E₁

              E2 = -50.0 - 31.10

               E2 = -81.10 N /C

we calculate the charge

             Q = E2 / 23.04 10⁹

             Q = -81.1 / 23.04 10⁹

              Q = -3.52 10⁻⁹ C

for this case the charge is negative

Which of the following is not a valid use of your driver's license?
proof of your ability to operate a motor vehicle
O proof of your age
O proof of your residency
proof that you have liability insurance

Answers

Answer:

Proof that you have liability insurance

Explanation:

Answer: The answer is proof that you have liability insurance

Explanation:

3. Consider the motion of the object whose velocity-time graph is given
in the diagram. What is the net displacement of the object between times
t = 0 and t = 2?
Velocity-time graph
8
(m/s)
8
12 16
16 m
2 m
8 m
56 m

Answers

Answer:

16 m.

Explanation:

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

Initial velocity (u) = 0 m/s

Final velocity (v) = 8 m/s

Initial time (t1) = 0 sec

Final time (t2) = 2 secs

Net Displacement (ΔD) =?

Velocity is defined as the rate of change of the displacement of an object with time. Mathematically, it is expressed as:

Change in velocity (Δv) = change in displacement (ΔD) / change in time (Δt)

Δv = ΔD / Δt

Next we shall determine the change in velocity and time. This is illustrated below below:

Initial velocity (u) = 0 m/s

Final velocity (v) = 8 m/s

Change in velocity (Δv) =?

Change in velocity (Δv) = v – u

Change in velocity (Δv) = 8 – 0

Change in velocity (Δv) = 8 m/s

Initial time (t1) = 0 sec

Final time (t2) = 2 secs

change in time (Δt) =?

change in time (Δt) = t2 – t1

change in time (Δt) = 2 – 0

change in time (Δt) = 2 secs.

Finally, we shall determine the net displacement of the object as follow:

Change in velocity (Δv) = 8 m/s

change in time (Δt) = 2 secs.

Net Displacement (ΔD) =?

Δv = ΔD / Δt

8 = ΔD/2

Cross multiply

ΔD = 8 × 2

ΔD = 16 m

Therefore, the net displacement of the object is 16 m.

A car stops in 120 m. If it has an acceleration of –5m/s 2 , how long did it take to stop

Answers

Answer:

t=240s

Explanation:

Distance=120m

Acceleration=-5m/s^2

v=0

Let u=x m/s

Using equation v^2-u^2=2as:-

0-x=2(-5)(120)

-x=-1200

x=1200m/s

Using now equation v=u+at:-

0=1200+-5t

5t=1200

t=240s

If a car stops at 120 meters. If it has an acceleration of –5 meters/second², then it would take  6.928 seconds to stop.

What is acceleration?

The rate of change of the velocity with respect to time is known as the acceleration of the object.

As given in the problem a car stops at 120 meters. If it has an acceleration of –5 meters/second², then we have to find out how long it would take seconds to stop.

By using the second equation of motion,

s = ut + 1/2at²

The distance traveled by car before stopping = 120 meters

acceleration =  –5 meters/second²

-120 = 0 + 0.5×( –5)t²

t² = 120/2.5

t² =48

t = 6.928 seconds

Thus, the time taken by the car before stopping would be 6.928 seconds.

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The average gorilla can travel 40.23 meters in 4 seconds, calculate the average speed in meters per second (m/s) 

Answers

Answer:

10.0575 m/s

Explanation:

40.23 divide by 4

Answer:

it is 10.0575 m/s

Explanation:

The average speed is calculated by total distance/total time taken. Here, the distance is 40.23 meters and time is 4 seconds.

So, average speed = 40.23/4 m/s

= 10.0575 m/s

The speed of a bus increases uniformly from
15 ms- to 60 ms in 20 seconds. Calculate
a. the average speed,
b. the acceleration,
C. the distance travelled during the entire
period The speed of a bus increases uniformly from
15 ms- to 60 ms in 20 seconds. Calculate
a. the average speed,
b. the acceleration,
C. the distance travelled during the entire
period​

Answers

Explanation:

a. For constant acceleration:

v_avg = ½ (v + v₀)

v_avg = ½ (60 m/s + 15 m/s)

v_avg = 37.5 m/s

b. a = (v − v₀) / t

a = (60 m/s − 15 m/s) / 20 s

a = 2.25 m/s²

c. x = v_avg t

x = (37.5 m/s) (20 s)

x = 750 m

what is the speed of a truck that travels 10 km in 10 minutes?

Answers

Answer:

10 minutes: 10 km

1 minute: 10 ÷ 10 = 1 km

the speed of the truck is 1km/min

Answer:

1 kilometer/minute

Explanation:

If we want to find the speed, we must divide the distance by the time.

[tex]s= \frac {s}{t}[/tex]

The truck travels a distance of 10 kilometers in 10 minutes.

[tex]d= 10 km\\t=10 min[/tex]

Substitute the values into the formula and divide.

[tex]s=\frac{d}{t}[/tex]

[tex]s=\frac{10 km}{10min}[/tex]

[tex]s= 1 km/min[/tex]

The speed of the truck is 1 kilometer per minute.

Hunk travelled 540 km at an average speed of 90 km/h. If Tim completed the same amount of distance with 1 hour and 30 min less than Hunk, what was Tim's average speed for the whole journey? km/h​

Answers

Answer:120

Explanation:it just is trust me

What is the Creation Mandate?​

Answers

is the divine injunction found in Genesis 1:28, in which God, after having created the world and all in it, ascribes to humankind the tasks of filling, subduing, and ruling over the earth.

4. A vehicle
accelerates from
0 km/h to
100 km/h in 10 s.
What is its average
acceleration?

Answers

Answer:

Average acceleration, [tex]a=2.77\ m/s^2[/tex]

Explanation:

Given that,

Initial velocity, u = 0 km/h

Final velocity, v = 100 km/h = 27.77 m/s

Time, t = 10 s

We need to find the average acceleration of the vehicle. It is given by the change in velocity divided by time. Som,

[tex]a=\dfrac{v-u}{t}\\\\a=\dfrac{27.77-0}{10}\\\\a=2.77\ m/s^2[/tex]

So, its average acceleration is [tex]2.77\ m/s^2[/tex].

A ski lift has a one-way length of 1 km and a vertical rise of 200 m. The chairs are spaced 20 m apart, and each chair can seat three people. The lift is operating at a steady speed of 10 km/h. Neglecting friction and air drag, and assuming that the average mass of each loaded chair is 250 kg, determine the power required to operate this ski lift. Also, estimate the power required to accelerate this ski lift in 17 s to its operating speed when it is first turned on.

Answers

Answer:

Explanation:

The question states that the chairs are spaced 20 m apart through a length of 1 km, or say, 1000 m.

It also does say that each chair weighs 250 kg, and as such the load is

M = 50 * 250

M = 12500.

Taking into consideration, the initial and final heights, we have

h1 = 0, h2 = 200 m

The work needed to raise the chairs,

W = mgh, where h = h2 - h1

W = 12500 * 9.81 * (200 - 0)

W = 2.54*10^7 J

The work is done at a rate of 10 km/h, and at a distance of 1 km, time taken would be

t = 1/10 = 0.1 h or say, 360 s

The power needed thus, is

P = W/t

P = 2.54*10^7 / 360

P = 68125 W, or 68 kW

Initial velocity, u = 0 m/s

Final velocity, v = 10 km/h = 2.78 m/s

Startup time, t is 17 s

Acceleration during the startup then is

a = (v - u)/t

a = 2.78/17

a = 0.163 m/s²

The power needed for the acceleration is

P = ½m [(v² - u²)/t]

P = ½ * 12500 * [2.78²/17]

P = 6250 * 0.455

P = 2844 W

Public television station KQED in San Francisco broadcasts a sinusoidal radio signal at a power of 777 kW. Assume that the wave spreads out uniformly into a hemisphere above the ground. At a home 5.00 km away from the antenna,
(a) what average pressure does this wave exert on a totally reflecting surface,
(b) what are the amplitudes of the electric and magnetic fields of the wave, and
(c) what is the average density of the energy this wave carries?
(d) For the energy density in part (c), what percentage is due to the electric field and what percentage is due to the magnetic field?

Answers

Answer:

A) P = 3.3 × 10^(-11) Pa

B) Amplitude of electric field = 1.931 N/C

Amplitude of magnetic field = 6.44 × 10^(-9) T

C) μ_av = 1.65 × 10^(-11) J/m³

D) 50% each for the electric and magnetic field

Explanation:

A) First of all let's calculate intensity.

I = P_av/A

We are given;

P_av = 777 KW = 777,000 W

Distance = 5 km = 5000 m

Thus;

I = 777000/(2π × 5000²)

I = 0.00495 W/m²

Now, the average pressure would be given by the formula;

P = 2I/C

Where C is speed of light = 3 × 10^(8) m/s

P = (2 × 0.00495)/(3 × 10^(8))

P = 3.3 × 10^(-11) Pa

B) Formula for the amplitude of the electric field is gotten from;

E_max = √[2I/(εo•c)].

Where εo is the Permittivity of free space with a constant value of 8.85 × 10^(−12) c²/N.mm²

I and c remain as before.

Thus;

E_max = √[(2 × 0.00495)/(8.85 × 10^(−12) × 3 × 10^(8))]

E_max = √3.72881355932

E_max = 1.931 N/C

Formula for amplitude of magnetic field is gotten from;

B_max = E_max/c

B_max = 1.931/(3 × 10^(8))

B_max = 6.44 × 10^(-9) T

C) Formula for average density is;

μ_av = εo(E_rms)²

Now, E_rms = E_max/√2

Thus;

E_rms = 1.931/√2

μ_av = 8.85 × 10^(−12) × (1.931/√2)²

μ_av = 1.65 × 10^(-11) J/m³

D) The energy density for the electric and magnetic field is the same. So both of them will have 50% of the energy density.

The energy radiated per unit surface area (across all wavelengths) for a black body with temperature 2200. Use 5.67 x 10-8 for the Stefan-Boltzmann constant.The ____________ describes the power radiated from a black body in terms of its temperature. Specifically, the total energy radiated per unit surface area of a black body across all wavelengths per unit time is proportional to the fourth power of the black body's thermodynamic temperature

Answers

Answer:

Stefan-Boltzmann Law describes the power radiated from a black body in terms of its temperature. Specifically, the total energy radiated per unit surface area of a black body across all wavelengths per unit time is proportional to the fourth power of the black body's thermodynamic temperature

Explanation:

So we now know that

energy per unit area is = zigma x T^4

From this

T = temperature in kelvin

zigma is stefan boltzman constant

So

E/A = 5.67 x 10^-8 x (2200)⁴

= 1.33x 10^6 W/m^2

please help! find magnitude and direction (the counterclockwise angle with the +x axis) of a vector that is equal to a + c

Answers

Answer:

Option (2)

Explanation:

From the figure attached,

Horizontal component, [tex]A_x=A\text{Sin}37[/tex]

[tex]A_x=12[\text{Sin}(37)][/tex]

     = 7.22 m

Vertical component, [tex]A_y=A[\text{Cos}(37)][/tex]

    = 9.58 m

Similarly, Horizontal component of vector C,

[tex]C_x[/tex]  = C[Cos(60)]

     = 6[Cos(60)]

     = [tex]\frac{6}{2}[/tex]

     = 3 m

[tex]C_y=6[\text{Sin}(60)][/tex]

    = 5.20 m

Resultant Horizontal component of the vectors A + C,

[tex]R_x=7.22-3=4.22[/tex] m

[tex]R_y=9.58-5.20[/tex] = 4.38 m

Now magnitude of the resultant will be,

From ΔOBC,

[tex]R=\sqrt{(R_x)^{2}+(R_y)^2}[/tex]

   = [tex]\sqrt{(4.22)^2+(4.38)^2}[/tex]

   = [tex]\sqrt{17.81+19.18}[/tex]

   = 6.1 m

Direction of the resultant will be towards vector A.

tan(∠COB) = [tex]\frac{\text{CB}}{\text{OB}}[/tex]

                  = [tex]\frac{R_y}{R_x}[/tex]

                  = [tex]\frac{4.38}{4.22}[/tex]

m∠COB = [tex]\text{tan}^{-1}(1.04)[/tex]

             = 46°

Therefore, magnitude of the resultant vector will be 6.1 m and direction will be 46°.

Option (2) will be the answer.

A wildebeest runs with an average speed of 4.0\,\dfrac{\text m}{\text s}4.0 s m ​ 4, point, 0, start fraction, start text, m, end text, divided by, start text, s, end text, end fraction for 15\,\text s15s15, start text, s, end text. What was its distance travelled in meters?

Answers

Answer:

60m

Explanation:

Answer: 60

Explanation: I got it right on Khan

Gwen releases a rock at rest from the top of a 40-m tower. If g = 9.8 m/s2 and air resistance is negligible, what is the speed of the rock as it hits the ground?

Answers

Answer:

[tex]28\; \rm m \cdot s^{-1}[/tex].

Explanation:

Short Explanation

Apply the SUVAT equation [tex]\left(v^2 - u^2) = 2\, a \, x[/tex], where:

[tex]v[/tex] is the final velocity of the object,[tex]u[/tex] is the initial velocity of the object, [tex]a[/tex] is the acceleration (should be constant,) and[tex]x[/tex] is the displacement of the object while its velocity changed from [tex]v[/tex] to [tex]u[/tex].

Assume that going downwards corresponds to a positive displacement. For this question:

[tex]v[/tex] needs to be found.[tex]u = 0[/tex] because the rock is released from rest.[tex]a = g = 9.8 \; \rm m\cdot s^{-2}[/tex].[tex]x = 40\; \rm m[/tex].

Solve this equation for [tex]v[/tex]:

[tex]\displaystyle v = \sqrt{2\, a\, x + u^2} = \sqrt{2\times 9.8 \times 40} = 28\; \rm m \cdot s^{-1}[/tex].

In other words, the rock reached a velocity of [tex]28\; \rm m\cdot s^{-1}[/tex] (downwards) right before it hits the ground.

Explanation

Let [tex]v[/tex] be the velocity (in [tex]\rm m \cdot s^{-1}[/tex]) of this rock right before it hits the ground. Under the assumptions of this question, it would take a time of [tex]t = (v / 9.8)[/tex] seconds for this rock to reach that velocity if it started from rest and accelerated at [tex]9.8\; \rm m \cdot s^{-2}[/tex].

Note that under these assumptions, the acceleration of this rock is constant. Therefore, the average velocity of this rock would be exactly one-half the sum of the initial and final velocity. In other words, if [tex]u[/tex] denotes the initial velocity of this rock, the average velocity of this rock during the fall would be:

[tex]\displaystyle \frac{u + v}{2}[/tex].

On the other hand, [tex]u = 0[/tex] because this stone is released from rest. Therefore, the average velocity of this rock during the fall would be exactly [tex](v / 2)[/tex].

The displacement of an object over a period of time is equal to the length of that period times the average velocity over that period. For this rock, the length of this fall would be [tex]t = (v / 9.8)[/tex], while the average velocity over that period would be [tex](v / 2)[/tex]. Therefore, the displacement (in meters) of the rock during the entire fall would be:

[tex]\displaystyle \left(\frac{v}{2}\right) \cdot \left(\frac{v}{9.8}\right) = \frac{v^2}{19.6}[/tex].

That displacement should be equal to the change in the height of the rock, [tex]40\; \rm m[/tex]:

[tex]\displaystyle \frac{v^2}{19.6} = 40[/tex].

Solve for [tex]v[/tex]:

[tex]v = 28\; \rm m \cdot s^{-1}[/tex].

Once again, the speed of the rock would be [tex]28\;\rm m \cdot s^{-1}[/tex] right before it hits the ground.

An elevator moves downward in a tall building at a constant speed of 5.05 m/s. Exactly 5.75 s after the top of the elevator car passes a bolt loosely attached to the wall of the elevator shaft, the bolt falls from rest.
(a) At what time does the bolt hit the top of the still-descending elevator? (Assume the bolt is dropped at t = 0 s.)


(b) Estimate the highest floor from which the bolt can fall if the elevator reaches the ground floor before the bolt hits the top of the elevator. (Assume 1 floor ≌ 3 m.)

Answers

Answer:

Explanation:

The elevator is moving with uniform speed and bolt will fall with acceleration due to gravity g .

Displacement of elevator when bolt starts falling

= 5.05 x 5.75 = 29 m

Let after time t bolt reaches the elevator

in time t , displacement of bolt = 1/2 g t²

= .5 x 9.8 x t² = 4.9 t²

displacement of elevator = 5.05 t

position of elevator = 29 + 5.05 t

According to question ,

29 + 5.05 t = 4.9 t²

4.9 t² - 5.05 t - 29 = 0

t = 3 s approx .

b )

Distance covered by the bolt

= 1 /2 g t²

= .5 x 9.8 x 9

= 44.1 m

Bolt must have to fall from a height of 44.1 m

or in terms of floor it is

44.1 / 3 = 15 th floor .

An 85 kg skydiver is falling through the air at a constant speed of 195 km h-1. At what rate does air resistance remove energy from the skydiver?

Answers

Answer:

46041J

Explanation:

Using Energy lost= mgh

Changing to standard its we have

= 195*1000/3600=54.2m/s

So = 85*54.2*10= 46041J

Answer:

45167.15 J/s

Explanation:

mass of the man = 85 kg

The man's speed = 195 km/h = 195 x 1000/3600 = 54.167 m/s

The man's weight = mg

where

m is the mass

g is acceleration due to gravity = 9.81 m/s^2

weight = 85 x 9.81 = 833.85 N

The rate at which energy is removed from the man = speed x weight

==> 54.167 x 833.85 = 45167.15 J/s

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