Which is an example of convection currents?
marshmallows toasting over a campfire
a pot being heated by an electric burner
feet getting hot when stepping across sand
a radiator emitting warm air and drawing in cool air

Answer:

due to gravity.

Explanation:

.............

The strength of the electric field is 1.10×10^4 N/C.

The data is sent to us.

r = d/2 = 0.1/2 = 0.05 m, d = 10 cm = 0.1 m, and z = 17 cm = 0.17 m

Q = 40 nC = 40×10^-9 C

A) in the middle of the two circles

Since the electric fields created by the two rings are directed in opposite directions, there is no electric strength.

B) midway down the left ring

Electric strength is equal to the sum of the electric fields created by the left and right rings.

Electric strength is equal to E leftring + E rightring, which equals 0 plus kQz/(r2 + z2).

Electric strength = k×Q×z/(r^2 + z^2)^

Electric strength = 9×10^9×40×10^-9×0.17/(0.05^2 + 0.17^2)

Electric strength= 1.10×10^4 N/C

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Answer:

a. 14000

Explanation:

Given parameters:

Efficiency of the machine  = 70%

Work done on machine  = 20000J

Unknown:

Work done by machine = ?

Solution:

 Efficiency of a machine is determined by;

  Efficiency  = [tex]\frac{Work done by machine}{Work done on machine} x 100[/tex]  

   70  = [tex]\frac{Work done by machine}{20000}[/tex] x 100

   70  = [tex]\frac{work done by machine}{200}[/tex]  

 Work done by machine  = 70 x 200 = 14000J

Answer:

the number of grains in the ball is 274,848

Explanation:

Given that;

diameter = 0.5 mm

so radius r = 0.25 mm

first we determine the volume of the ball using the following equation;

V = 4/3×πr³

we substitute

V = 4/3×π(0.25)³

V =  0.06544 mm³

Now form table 1.1 "Grain sizes" a metal with grain size number of 12 has about 4,200,000 grains/mm³

so;

Number of grains N = 0.06544 × 4,200,000

N = 274,848 grains

Therefore, the number of grains in the ball is 274,848

The object changes direction when its velocity changes sign. You can get the velocity function by differentiating the position function with respect to time t :

x(t) = 4t ² - 41t + 78

→   v(t) = dx(t)/dt = 8t - 41

Solve v(t) = 0:

8t - 41 = 0

8t = 41

t = 41/8 = 5.125

Just to confirm that the velocity indeed changes sign:

• Pick any time before this one to check the sign of v :

v (0) = 8•0 - 41 = -41 < 0

• Pick any time after and check the sign again:

v (6) = 8•6 - 41 = 7 > 0

Now just find the position at this time:

x (5.125) = -433/16 = -27.0625

which means the object is 27.0625 units on the negative x-axis.

You can also do this without calculus by completing the square in the position function:

4t ² - 41t + 78 = 4 (t ² - 41/4 t ) + 78

… = 4 (t ² - 2• 41/8 t + (41/8)² - (41/8)²) + 78

… = 4 (t ² - 2• 41/8 t + (41/8)²) - 4•1681/64 + 78

… = 4 (t - 41/8)² - 433/16

which describes a parabola that opens upward. When t = 41/8 = 5.125, the quadratic term vanishes and the turning point of the parabola occurs at a position of -433/16 units.

Answer:

B: The scale reading will increase momentarily then will decrease as the student is moving upward from the scale

Explanation:

The way weighing scale works is that when you climb on it, it will take your weight reading but when you are moving off the top of it, the reading slowly approaches 0 until you are completely off it.

Thus, the lab partner will observe that the reading will increase for a while and then gradually decrease to zero as the student moves upwards off the scale.

The correct answer is (B)The scale reading will increase momentarily then will decrease as the student is moving upward from the scale.

According to the third law of motion, every action has an equal and opposite reaction. In order to jump, the student will apply force to the bathroom scale in downward direction and there will be an equal force exerted by the bathroom scale upwards on the student which helps him jump.

 So when the student applies downward force on the scale in order to jump, the scale reading will increase momentarily and then will decrease as the student moves upwards.

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Answer:

Velocity of the box: 10.67 m/s

Explanation:

Recall that impulse is defined as the force applied times the time the force is in action. Then we can obtained the value of the impulse given to the box as:

Impulse = F * time = 33.3 N * 2.35 s = 78.225 kg m/s

then we use the momentum of the box at that precise time to find its velocity recalling that :

Momentum = mass * velocity

Then

78.225 kg m/s = 7.33 kg * v

v = 78.225/7.33  m/s = 10.67 m/s

Answer:

I = mgd/4π²f²

Explanation:

The period of the physical pendulum T = 1/f where f = frequency,

T = 1/f = 2π√(I/mgd) where I = moment of inertia of the physical pendulum, m =mass of pendulum, g = acceleration due to gravity and d = distance of center of mass of pendulum from pivot point.

1/f = 2π√(I/mgd)

dividing both sides by 2π, we have

1/2πf = √(I/mgd)

squaring both sides, we have

(1/2πf) = [√(I/mgd)]²

1/4π²f² = I/mgd

multiplying both sides by mgd, we have

I = mgd/4π²f²

Answer:

Δp = 620 N.s

Explanation:

       [tex]F = \frac{\Delta p}{\Delta t} (1)[/tex]

       for m= constant, it reduces to F= m*a.

       [tex]\Delta p = F* \Delta t = 62 N* 10.0 s = 620 N*s (2)[/tex]

Answer:

146.27 m

Explanation:

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

Velocity of tourist (vₜ) = 4.65 m/s

Distance travelled by tourist (dₜ) = d

Velocity of bear (v₆) = 5.68 m/s

Distance travelled by bear (d₆) = 32.4 + d

Value of d =?

Next, we shall determine the time taken for tourist and the bear to get to the car.

For the tourist:

Velocity of tourist (vₜ) = 4.65 m/s

Distance travelled by tourist (dₜ) = d

Time (tₜ) =?

vₜ = dₜ / tₜ

4.65 = d/tₜ

Cross multiply

4.65 × tₜ = d

Divide both side by 4.65

tₜ = d / 4.65

For the bear:

Velocity of bear (v₆) = 5.68 m/s

Distance travelled by bear (d₆) = 32.4 + d

Time (t₆) =?

v₆ = d₆ / t₆

5.68 = (32.4 + d) / t₆

Cross multiply

5.68 × t₆ = (32.4 + d)

Divide both side by 5.68

t₆ = (32.4 + d) / 5.68

NOTE: Both the tourist and the bear have the same time. Thus, to obtain the value of d, we shall equate both the time taken for the tourist and the bear together. This is illustrated below:

Time taken by tourist (tₜ) = time taken by the bear (t₆)

tₜ = d / 4.65

t₆ = (32.4 + d) / 5.68

tₜ = t₆

d / 4.65 = (32.4 + d) / 5.68

Cross multiply

d × 5.68 = 4.65 (32.4 + d)

5.68d = 150.66 + 4.65d

Collect like terms

5.68d – 4.65d = 150.66

1.03d = 150.66

Divide both side by 1.03

d = 150.66 / 1.03

d = 146.27 m

Thus, the maximum value of d is 146.27 m

Answer: Location the data and observations collected in your lab guide

Explanation:

Answer:

Follows are the solution to this question:

Explanation:

Energy shifts at such a rollercoaster ride many times throughout a ride from possibility to dramatic power. Kinetic energy is the energy the object provides for its movement. The coaster machine is traditionally lifted by a rope from the very first hill. It gains energy stored because as vehicles move up.

OR

we can say that whenever anyone travels through an amusement park ride often recognized as a ring road, energy transfers from the opportunity to kinetic energy, because of the layout of the curves as well as the slope, and it is replicated few more occasions during the ride.

Kinetic energy seems to be used in motion.

Its amusement ride vehicles were usually climbed back by a rope from the very first hill, but as the other vehicles move along that route, they acquire potential power.  

Answer:

See the explanation below.

Explanation:

We have to take into account that the potential difference is equal to the voltage, and this is measured between two points as the resistors are connected in parallel to the voltage source, the resistors will have the same voltage.

For ease, we will take the attached image of resistors connected in parallel.

As both resistors at their ends share the A & B connection points, these are at a voltage of 12V

Answer:

Gravitation Potential Energy and Elastic Potential Energy

Explanation:

PE=abbreviation for potential energy

PE is a mechanical energy like KE is. There are two types of PE in high school physics (do not talk about other PE's like chemical PE).

Elastic PE is like the stored energy for example in a pole vault competition, the Elastic PE is stored in the pole before the vaulter goes over the desired height. (Energy stored in ELASTIC object ONLY) (commonly on the 11th grade regents springs are used to represent elastic PE)

Gravitational PE can be calculated through the formula PE=mgh although some people substitute the PE with a U. (ENERGY STORED IN OBJECT'S HEIGHT)

Answer:

3k mph

Explanation:

don't take my answer it is wrong

Answer:

B. contain hydrogen

C. clouds of gas and dust

E. needed to create a star

Explanation:

A star is a giant astronomical or celestial object that is comprised of a luminous sphere of plasma, binded together by its own gravitational force.

Some of the examples of stars are; Vega, Sun (closest to planet Earth), Antares, Betelgeus, Canopus, etc.

Stars are typically made up of two (2) main hot gas, Hydrogen (H) and Helium (He). The chronological order in which the formation of a star occur are;

1. Gravity pulls gas and dust together to form dense cores.

2. A protostar forms as mass increases.

3. Nuclear fusion begins under high pressure.

Scientists have been able to understand and discover that, gravity pulled materials (low-density cloud of interstellar gas and dust known as a nebula) together forming the planetary bodies in our solar system.

A dark nebula can be defined as an interstellar cloud that is so dense as a result of high concentration of gas and dust and as such it obscures the visible wavelengths of light from stars behind it, thus appearing completely opaque (dark patch) in front of a bright emission nebula or in regions having plenty stars.

The characteristics of a nebulae are;

I. It contain hydrogen.

II. Clouds of gas and dust

III. It is needed to create a star.

Answer:

Force that acted on the body was F = 13 N

Explanation:

If once accelerated, the body covers 60 meters in 6 seconds, then its velocity is 60/6 m/s = 10 m/s

When the force was acting (for 10 seconds) the object accelerated from rest (initial velocity vi = 0) to 10 m/s (its final velocity). therefore we can use the kinematic equation for the velocity in an accelerated motion given by:

[tex]v_f=v_i+a*t[/tex]

which in our case becomes;

[tex]10\,m/s=0+a*(10\,s)[/tex]

and we can solve for the acceleration as:

a = 10/10  m/s^2 = 1 m/s^2

Therefore the force acting on the body, based on Newton's 2nd Law expression: F = m * a is:

F = 13 kg * 1 m/s^2 = 13 N

Answer:

1 and 3

Explanation:

Scientists can use the following techniques to determine the characteristics of Earth's layers: a) conduct experiments on how minerals change under high pressure; and b) investigate how seismic waves travel through different layers.

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Answer:

The magnitude of the maximum net force on the object during the motion is 16 newtons.

Explanation:

The position of the mass, measured in meters, within the mass-spring system is:

[tex]x(t) = A\cdot \cos \left(\omega\cdot t \right)[/tex] (1)

Where:

[tex]A[/tex] - Amplitude, measured in meters.

[tex]t[/tex] - Time, measured in seconds.

[tex]\omega[/tex] - Angular frequency, measured in radians per second.

The acceleration function ([tex]\ddot {x} (t)[/tex]), measured in meters per square second, is obtained by deriving twice (1) in time:

[tex]\dot {x} (t) = -\omega\cdot A\cdot \sin (\omega\cdot t)[/tex]

[tex]\ddot {x} (t) = -\omega^{2}\cdot A\cdot \cos (\omega\cdot t)[/tex] (2)

And the maximum acceleration ([tex]a_{max}[/tex]), measured in meters per square second, experimented by the mass is:

[tex]a_{max} = \omega^{2}\cdot A[/tex] (3)

And the maximum net force ([tex]F[/tex]), measured in newtons, is:

[tex]F = m\cdot a_{max}[/tex] (4)

If we know that [tex]\omega = 2\,\frac{rad}{s}[/tex], [tex]A = 0.80\,m[/tex] and [tex]m = 5\,kg[/tex], then the maximum net force on the object during the motion is:

[tex]a_{max} = \left(2\,\frac{rad}{s} \right)^{2}\cdot (0.80\,m)[/tex]

[tex]a_{max} = 3.2\,\frac{m}{s^{2}}[/tex]

[tex]F = (5\,kg)\cdot \left(3.2\,\frac{m}{s^{2}} \right)[/tex]

[tex]F = 16\,N[/tex]

The magnitude of the maximum net force on the object during the motion is 16 newtons.

The magnitude of the maximum net force on the object during the motion will be 16 newtons.

Force is defined as the push or pull applied to the body. Sometimes it is used to change the shape, size, and direction of the body. Force is defined as the product of mass and acceleration. Its unit is Newton.

The given data in the problem is;

m is the mass of  5.0 of object kg

x (t ) = A cos(ωt ),

A is the amplitude=  0.80 m

ω is the frequency= 2.0 s-1 .

F is the  magnitude of the maximum net force=?

The position of the mass is given by the equation;

[tex]x(t)= A cos( \omega t)[/tex]]

[tex]\em \dot x= - \omega A sin(\omega t) \\\\ \dot \dot x = - \omega ^2 A cos (\omega t)[/tex]

The maximum acceleration is found as;

[tex]\rm a_{max} = \omega ^2 A \\\\ \rm a_{max} = (2) ^2 \times 0.80 \\\\ \rm a_{max} =3.2 \m/sec^2[/tex]

The value of net force is found as;

[tex]\rm F= m a_{max} \\\\ \rm F= 5 \times 3.2 \\\\\ \rm F=16\ N \\[/tex]

Hence the magnitude of the maximum net force on the object during the motion will be 16 newtons.

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Answer:

Psychology traces its roots back through recorded history to India, China, the Middle East, and Europe. Buddha and Confucius focused on the powers and origin of ideas. ... The ideas of Bacon and Locke contributed to the development of modern empiricism.

Explanation:

Answer:

Relative dating is used to determine a fossils approximate age by comparing it to similar rocks and fossils of known ages. Absolute dating is used to determine a precise age of a fossil by using radiometric dating to measure the decay of isotopes, either within the fossil or more often the rocks associated with it.

Answer:

Resistivity = 231.481 K Ohm

Yes, Intrinsic Silicon is the semiconductor.

Explanation:

Solution:

At 300K:

Let suppose mobility of electron in intrinsic semiconductor = [tex]M_{e}[/tex]

Mobility of electron in intrinsic semiconductor is:

[tex]M_{e}[/tex]  = 1300 [tex]cm^{2}[/tex]/volt.sec

Let suppose mobility of hole in intrinsic semiconductor = [tex]M_{h}[/tex]

[tex]M_{h}[/tex] = 500 [tex]cm^{2}[/tex]/volt.sec

We know that, intrinsic silicon semiconductor has equal number of holes and electrons. So,

At 300 K

Intrinsic Carrier Concentration = 1.5 x [tex]10^{10}[/tex]/[tex]cm^{3}[/tex] = C

And,

Conductivity of intrinsic Silicon is:

σ = C x ([tex]M_{h}[/tex] + [tex]M_{e}[/tex]) e

e = 1.6 x [tex]10^{-19}[/tex] C

So, plugging in the values, we get:

σ = C x ([tex]M_{h}[/tex] + [tex]M_{e}[/tex]) e

σ = 1.5 x [tex]10^{10}[/tex] x (500 + 1300) x 1.6 x [tex]10^{-19}[/tex]

σ = 4.32 x [tex]10^{-6}[/tex]

So, now we can find the resistivity.

Resistivity = 1/σ

Resistivity = 1/ 4.32 x [tex]10^{-6}[/tex]

Resistivity = 231.481 K Ohm

Yes, Intrinsic Silicon is the semiconductor.

Answer:

26 m southwards.

Explanation:

From a North, East, South, West coordinate plane, moving northwards implies positive distance. While moving southwards implies negative distance.

Thus;

It moves 16 meters northward; d = 16 m

It now moves 22 meters southward; d = -22 m

It moves 12 meters northward; d = 12 m

It moves 32 meters southward; d = -32 m

Thus, total magnitude = 16 - 22 + 12 - 32 = -26 m

Thus, the object travels 26 m southwards.

Answer: The more massive one will have larger kinetic energy.

Explanation:

We know that when we drop an object, the acceleration of the object will be equal to the gravitational acceleration.

a(t) = -9.8m/s^2

And to get the velocity, we need to integrate over time, to get:

v(t) = (-9.8m/s^)*t + v0

Where v0 is the initial speed of the object.

You can see that the mass of the object does not affect the velocity of it.

Then when we drop two marbles of different masses from the same height, we know that the final velocity of them will be equal.

Now, we also know that the kinetic energy can be written as:

K = (m/2)*v^2

where m is the mass, and v is the velocity.

Then the kinetic energy of the marble with less mass can be written as:

k = (m/2)*v^2

And the kinetic energy for the more massive one is:

K = (M/2)*v^2

And we know that both of them have the same velocity, and M is larger than m, then we can conclude that the marble with larger mass will have larger kinetic energy.

Answer:

Explanation:

The speed will remain unchanged because speed does not depend upon frequency .

So new speed = v

wavelength x frequency = speed

For frequency = 2 f

wavelength = speed / frequency

= v / 2f

So new wavelength = v / 2f .

1. The new wavelength is equal to [tex]\frac{\lambda}{2}[/tex].

2. The new speed is equal to v.

Given the following data:

To determine the new wavelength and new speed are:

Mathematically, the speed of a waveform is calculated by using the formula;

[tex]v = \lambda f[/tex]

Where:

Ideally, the speed of a wave doesn't change when the frequency provided they are both in the same medium.

However, the wavelength would change when frequency changes.

Therefore, the new speed = v.

For new wavelength:

[tex]v = \lambda f=\frac{\lambda}{2} (2f)[/tex]

New wavelength = [tex]\frac{\lambda}{2}[/tex]

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Answer: 20

Explanation: cause

Explanation:

When two or more atoms link up, they create a molecule. e.g, A molecule of water is made of two atoms of hydrogen (H) and one atom of oxygen (O).

Answer:

2.61 atm

Ley de Boyle

Explanation:

[tex]P_1[/tex] = Presión inicial = 0.96 atm

[tex]P_2[/tex] = Presión final

[tex]V_1[/tex] = Volumen inicial = 95 mL

[tex]V_2[/tex] = Volumen final = 35 mL

En este problema usaremos la ley de Boyle.

[tex]\dfrac{P_1}{P_2}=\dfrac{V_2}{V_1}\\\Rightarrow P_2=\dfrac{P_1V_1}{V_2}\\\Rightarrow P_2=\dfrac{0.96\times 95}{35}\\\Rightarrow P_1=2.61\ \text{atm}[/tex]

La presión ejercida sobre el émbolo para reducir su volumen es de 2.61 atm.

Answer: C. A stove burner that glows red when it is turned on

Explanation:

I did the quiz