Answer:
Charging by contact is when the charged object is brought near but never contacted to the object being charged
Explanation:
If i push a ball along the floor, which forces are acting upon the ball? Name atleast two forces and explain them !
Answer:
Hey there!
You are applying a force, pushing the ball, which makes the ball move forwards.
Friction is working in the opposite direction, slowing the ball down as it rolls on the floor.
Let me know if this helps :)
Two strings are respectively 1.00 m and 2.00 m long. Which of the following wavelengths, in meters, could represent harmonics present on both strings?
1) 0.800, 0.670, 0.500
2) 1.33, 1.00, 0.500
3) 2.00, 1.00, 0.500
4) 2.00, 1.33, 1.00
5) 4.00, 2.00, 1.0
Answer:
5) 4.00, 2.00, 1.0
Explanation:
wave equation is given as;
F₀ = V / λ
Where;
F₀ is the fundamental frequency = first harmonic
Length of the string for first harmonic is given as;
L₀ = (¹/₂) λ
λ = 2 L₀
when L₀ = 1
λ = 2 x 1 = 2m
when L₀ = 2m
λ = 2 x 2 = 4m
For First harmonic, the wavelength is 2m, 4m
For second harmonic;
L₁ = (²/₂)λ
L₁ = λ
When L₁ = 1
λ = 1 m
when L₁ = 2
λ = 2 m
For second harmonic, the wavelength is 1m, 2m
Thus, the wavelength that could represent harmonics present on both strings is 4m, 2m, 1 m
A truck pulls a block 8 meters across a level surface at a force of 216 N over the course of 12 seconds. How much power did the truck use
Answer:
work = 1728
Power = 134
Explaination:
by using the formula,
Work(W)= Force(F)×Distance(D)
andPower(P)= Work(W)/Time taken(T)
A speeding motorist traveling down a straight highway at 100 km/h passes a parked police car. It takes the police constable 1.0 s to take a radar reading and to start up his car. The police vehicle accelerates from rest at 2 m/s2 and finally catches up with the speeder. a) How much time has elapsed when the two cars meet?
Answer:
t = 7.5 s
Explanation:
The distance traveled by the car at the time of meeting of the two cars must be the same. First, we calculate the distance traveled by the police car. For that we use 2nd equation of motion. Here, we take the time when police car starts to be reference. So,
s₁ = Vi t + (0.5)gt²
where,
s₁ = distance traveled by police car
Vi = Initial Velocity = 0 m/s
t = time taken
Therefore,
s₁ = (0 m/s)(t) + (0.5)(9.8 m/s²)t²
s₁ = 4.9 t²
Now, we calculate the distance traveled by the car. For constant speed and time to be 1 second more than the police car time, due to car starting time, we get:
s₂ = Vt = V(t + 1)
where,
s₂ = distance traveled by car
V = Velocity of car = (100 km/h)(1000 m/1 km)(1 h/ 3600 s) = 27.78 m/s
Therefore,
s₂ = 27.78 t + 27.78
Now, we know that at the time of meeting:
s₁ = s₂
4.9 t² = 27.78 t + 27.78
4.9 t² - 270.78 t - 27.78 = 0
solving the equation and choosing the positive root:
t = 6.5 s
since, we want to know the time from the moment car crossed police car. Therefore, we add 1 second of starting time in this.
t = 6.5 s + 1 s
t = 7.5 s
A 100-kg tackler moving at a speed of 2.6 m/s meets head-on (and holds on to) an 92-kg halfback moving at a speed of 5.0 m/s. Part A What will be their mutual speed immediately after the collision? Express your answer to two significant figures and include the appropriate units.
Given that,
Mass of trackler, m₁ = 100 kg
Speed of trackler, u₁ = 2.6 m/s
Mass of halfback, m₂ = 92 kg
Speed of halfback, u₂ = -5 m/s (direction is opposite)
To find,
Mutual speed immediately after the collision.
Solution,
The momentum of the system remains conserved in this case. Let v is the mutual speed after the collision. Using conservation of momentum as :
[tex]m_1u_1+m_2u_2=(m_1+m_2)V\\\\V=\dfrac{m_1u_1+m_2u_2}{(m_1+m_2)}\\\\V=\dfrac{100\times 2.6+92\times (-5)}{(100+92)}\\\\V=-1.04\ m/s[/tex]
So, the mutual speed immediately after the collision is 1.04 m/s but in opposite direction.
What effect does the velocity of a rotating object have on the centripetal force exerted on it?
Answer:
The velocity of a rotating object and the centripetal force exerted on it are proportional to each other. Centripetal force is equal to mv /r. If the velocity increases, the centripetal force increases as well.
Explanation:
The velocity has the direct effect on the centripetal force. Hence, increasing the velocity, centripetal force also increases or vice - versa.
The given problem is based on the basic concept of centripetal force and fundamentals involved in the centripetal force. The centripetal force is a center seeking force which comes to play, when any object undergoes the rotational motion around the circular path.
The mathematical expression for the centripetal force is given as,
[tex]F= \dfrac{mv^{2}}{r}[/tex]
Here,
m is the mass of an object.
v is the velocity of an object undergoing the motion around the circular path.
r is the radius of curvature.
From the concept of centripetal force, the velocity of a rotating object and the centripetal force exerted on it are proportional to each other. Centripetal force is equal to mv /r. If the velocity increases, the centripetal force increases as well.
Thus, we can conclude that the velocity has the direct effect on the centripetal force. Hence, increasing the velocity, centripetal force also increases or vice - versa.
Learn more about the centripetal force here:
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pls help me solve dis
Answer:
9 Ω
Explanation:
The following data were obtained from the question:
Resistor 1 (R1) = 3 Ω
Resistor 2 (R2) = 3 Ω
Resistor 3 (R3) = 3 Ω
Resistor 4 (R4) = 3 Ω
Resistor 5 (R5) = 3 Ω
Resistor 6 (R6) = 3 Ω
Resistor 7 (R7) = 3 Ω
Resistor 8 (R8) = 3 Ω
Resistor 9 (R9) = 3 Ω
Resistor 10 (R10) = 3 Ω
Resistor 11 (R11) = 3 Ω
Resistor 12 (R12) = 3 Ω
Equivalent Resistance (R) =.?
From the above diagram,
Resistor 1, 2, 3, 4, 5 and 6 are in series connection and in parralle connections with Resistor 7, 8, 9, 10, 11 and 12 which are also in series connection.
Thus we shall determine the equivalent resistance of Resistor 1, 2, 3, 4, 5 and 6
This is illustrated below:
Resistance Ra = R1 + R2 + R3 + R4 + R5 + R6
Ra = 3 + 3 + 3 + 3 + 3 + 3
Ra = 18 Ω
Next, we shall determine the equivalent resistance of Resistor 7, 8, 9, 10, 11 and 12.
This is illustrated below:
Resistance Rb = R7 + R8 + R9 + R10 + R11 + R12
Rb = 3 + 3 + 3 + 3 + 3 + 3
Rb = 18 Ω
Thus, Ra and Rb are in parallel connections. The equivalent resistance between A and B can be obtained as shown below :
Ra = 18 Ω
Rb = 18 Ω
Equivalent resistance R =?
1/R = 1/Ra + 1/Rb
1/R = 1/18 + 1/18
1/R = 2/18
1/R = 1/9
Invert
R = 9 Ω
Therefore, the equivalent resistance between A and B is 9 Ω.
you have one 100 ohm resistor what size resistor must you hook up in parallel in order to have a resistance of 99.0
Answer:
The resistor to be hooked up must be 9900 [tex]\Omega[/tex]
Explanation:
Recall how resistors in parallel combine to render an equivalent resistor:
[tex]\frac{1}{R_e} =\frac{1}{R_1} +\frac{1}{R_2}[/tex]
So we need to find which resistor (R2) we need to combine in parallel with resistor R1 (100 [tex]\Omega[/tex]) in order to obtain an equivalent resistor Re (99 [tex]\Omega[/tex]) :
[tex]\frac{1}{99} =\frac{1}{100} +\frac{1}{R_2}\\\frac{9900\,R_2}{99} =\frac{9900\,R_2}{100} +\frac{9900\,R_2}{R_2}\\100\,R_2= 99\,R_2+9900\\R_2=9900\,\,\Omega[/tex]
A small candle is 34 cm from a concave mirror having a radius of curvature of 22 cm. Where will the image of the candle be located? Follow the sign conventions.
Answer:
16.26 cm in front of the mirror
Explanation:
Using,
1/f = 1/u+1/v....................... Equation 1
Where f = focal focal length of the concave mirror, u = object distance, v = image distance.
make v the subject of the equation
v = fu/(u-f)................... Equation 2
Note: The focal length of a concave mirror is positive
Using the real- is- positive convention
Given: f = 22/2 = 11 cm, u = 34 cm.
Substitute into equation 2
v = (34×11)/(34-11)
v = 374/23
v = 16.26 cm.
The image will be formed 16.26 cm in front of the mirror.
The coefficient of static friction between a 3.00 kg crate and the 35.0o incline is 0.300. What minimum force F must be applied perpendicularly to the incline to prevent the crate from sliding down
Answer:
32.13 N
Explanation:
Given that
mass of the crate, m = 3 kg
angle of inclination, = 35°
coefficient of static friction, = 0.3
To solve this, we can assume that the minimum force is F Newton, then use the formula
mgsinA = coefficient of static friction * [F + mgcosA]
=>3 * 9.8 * sin35 = 0.3 * [F + 3 * 9.8 * cos35]
=> 29.4 * 0.5736 = 0.3 * [F + 29.4 * 0.8192]
=> 16.86 = 0.3 [F + 24.08]
=> 16.86 = 0.3F + 7.22
=> 16.86 - 7.22 = 0.3F
=> 0.3F = 9.64
=> F = 9.64/0.3
=> F = 32.13 N
Therefore, the Force that must be applied is 32.13 N
The net force that must be applied is 9.8 N.
The minimum force required is Fnet.
Fnet = -Ff + mgsinθ
But Ff = μN = μmgcosθ
Fnet = - μmgcosθ + mgsinθ
Where;
m = 3.00 kg
μ = 0.300
θ = 35.0o
Substituting values;
Fnet = mgsinθ - μmgcosθ
Fnet = (3 × 10 × sin 35.0o) - (3 × 0.300 × 10 × cos 35.0o)
= 17.2 - 7.4
Fnet = 9.8 N
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A 5.0 V battery storing 43.0 kJ of energy supplies 1.5 A of current to a circuit. How much energy does the battery have left after powering the circuit for 1.0 h? A. 43 kJ B. 16 kJ C. 41 kJ D. 27 kJ
Answer:
B. 16 kJ
Explanation:
Energy = VIt.............. Equation 1
Where V = Voltage, I = Current, t = time
Given: V = 5.0 V, I = 1.5 A, t = 1 h = 3600 s.
Substitute these values into equation 2
E = 5.0(1.5)(3600)
E = 27000 J
E = 27 kJ.
Amount of energy left = 43 kJ - 27 kJ
Amount of energy left = 16 kJ.
Hence the right option is B. 16 kJ
What quantity, combined with universal physical quantities, can be used to determine a particle's de Broglie wavelength
Answer:
The quantity that will be combined to determine a particle's de Broglie wavelength is ENERGY.
Explanation:
Energy of a particle is given by;
E = hf
Where;
f is frequency of the particle's wave = c/λ
[tex]E = \frac{hc}{\lambda}[/tex]
[tex]\lambda= \frac{hc}{E}[/tex]
Where;
λ is the particle's de Broglie wavelength
h is the Planck's constant = 6.626 x 10⁻³⁴ J/s (This is one of the universal physical quantities)
c is the speed of light, = 3 x 10⁸ m/s (This is also one of the universal physical quantities)
E is the energy of the particle.
Therefore, the quantity that will be combined to determine a particle's de Broglie wavelength is ENERGY.
The de Broglie wavelength of a particle can be calculated using energy and universal physical parameters.
Define wavelength.The wavelength of a wave signal conveyed in space or down a wire is the distance among identical points (consecutive crests) in adjacent cycles.
When two persons have the same overall mentality and hence can communicate successfully, this is an instance of wavelength.
The de Broglie wavelength of a particle can be calculated using energy and universal physical parameters.
Find out more information about wavelength here:
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Calculate the period of a satellite orbiting the Moon, 98 kmkm above the Moon's surface. Ignore effects of the Earth. The radius of the Moon is 1740 kmkm.
Answer:
3.6*10^18s
Explanation:
To find the period of the satellite
We need to apply kephler's third law
Which is
MP² = (4π²/G) d³
d=semi-major axis which is the distance from center of moon = 98km+1740km = 1838km
where M= mass of the moon = 7.3x10^22kg
P=period
G=newtonian gravatational constant= 6.67x10^-11
To find the Period solve for P
P = √[(4π²/G M)xd³]
P=√(4 π²/6.67x10^-22*7.3x10^22kg) x (1.838x10^6m)³]
= 3.6*10^18s
A Carnot heat engine and an irreversible heat engine both operate between the same high temperature and low temperature reservoirs. They absorb the same energy from the high temperature reservoir as heat. The irreversible engine:__________. A. does more work. B. has the same efficiency as the reversible engine. C. has the greater efficiency. D. transfers more energy to the low temperature reservoir as heat. E. cannot absorb the same energy from the high temperature reservoir as heat without violating the second law of thermodynamics.
Answer:
the answers d
A Carnot heat engine and an irreversible heat engine both operate between the same high-temperature and low-temperature reservoirs. They absorb the same energy from the high-temperature reservoir as heat. The irreversible engine cannot absorb the same energy from the high-temperature reservoir as heat without violating the second law of thermodynamics, therefore the correct option is E.
What is a Carnot engine?It is a theoretical engine assumed to have the maximum efficiency among all engines out there in the universe.
No other engine can have greater efficiency than the Carnot engine.
The Carnot engine work on the principle of the Carnot cycle which assume that the heat and work tranfer processes are reversible in nature. there is no loss due to the friction of the piston.
As we know from the second law of thermodynamics that no other engine can have greater efficiency than the Carnot engine.
Thus, the irreversible engine cannot absorb the same energy from the high-temperature reservoir as heat without violating the second law of thermodynamics, therefore the correct option is E.
Learn more about the Carnot engine from here
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If the plane travels at 600 km/h for 2 hours, how far has it traveled?
Explanation:
Distance = speed × time
d = (600 km/hr) (2 hr)
d = 1200 km
In the growth stage of a product's life cycle, demand has its own momentum through word of mouth and interactive marketing.
a. True
b. False
Answer:
Advertising, events and experiences, and personal selling all become more important in the maturity stage.
Explanation:
In the growth stage, demand has its own momentum through word of mouth and interactive marketing. hope this helps you :)
Why is a flask is wider on the bottom than on the top? allows for a more precise measurement allows for better thermal equilibrium prevents spillage to hold a thermometer
Answer:
allows for better thermal equilibrium
Explanation:
Due to the cone shape, most of the liquid will be closer to the bottom than the top. The large surface area of the bottom allows for faster heating.
A wheel that is rotating at 33.3 rad/s is given an angular acceleration of 2.15 rad/s 2. Through what angle has the wheel turned when its angular speed reaches 72.0 rad/s
Answer:
The angle through which the wheel turned is 947.7 rad.
Explanation:
initial angular velocity, [tex]\omega _i[/tex] = 33.3 rad/s
angular acceleration, α = 2.15 rad/s²
final angular velocity, [tex]\omega_f[/tex] = 72 rad/s
angle the wheel turned, θ = ?
The angle through which the wheel turned can be calculated by applying the following kinematic equation;
[tex]\omega_f^2 = \omega_i^2 + 2\alpha \theta\\\\\theta = \frac{\omega_f^2\ -\ \omega_i^2}{2\alpha } \\\\\theta = \frac{(72)^2\ -\ (33.3)^2}{2(2.15)}\\\\\theta = 947.7 \ rad[/tex]
Therefore, the angle through which the wheel turned is 947.7 rad.
Amy runs 2 blocks south, then turns around and runs 3 blocks north. what is the distance and displacement
Answer: Distance= 5 blocks and displacement= -1 block
Explanation: distance is the total length of a journey while displacement is the shortest straight length of a journey!
An electron accelerates through a 12.5 V potential difference, starting from rest, and then collides with a hydrogen atom, exciting the atom to the highest energy level allowed. List all the possible quantum-jump transitions by which the excited atom could emit a photon. 4 rightarrow 3 4 rightarrow 2 4 rightarrow 1 3 rightarrow 2 3 rightarrow 1 2 rightarrow 1
Answer:
Initial state Final state
3 ⇒ 2
3 ⇒ 1
2 ⇒ 1
Explanation:
For this exercise we must use Bohr's atomic model
E = - 13.606 / n²
where is the value of 13.606 eV is the energy of the ground state and n is the integer.
The energy acquired by the electron in units of electron volt (eV)
E = e V
E = 12.5 eV
all this energy is used to transfer an electron from the ground state to an excited state
ΔE = 13.6060 (1 / n₀² - 1 / n²)
the ground state has n₀ = 1
ΔE = 13.606 (1 - 1/n²)
1 /n² = 1 - ΔE/13,606
1 / n² = 1 - 12.5 / 13.606
1 / n² = 0.08129
n = √(1 / 0.08129)
n = 3.5
since n is an integer, maximun is
n = 3
because it cannot give more energy than the electron has
From this level there can be transition to reach the base state.
Initial state Final state
3 ⇒ 2
3 ⇒ 1
2 ⇒ 1
The possible quantum-jump transitions by which the excited atom emits a photon are :
Initial state Final state
3 ---> 2
3 ----> 1
2 ----> 1
Given data :
Potential difference through which an electron accelerates = 12.5 V
Energy acquired by the the electrons = 12.5 eV ( e * 12.5 )
The Model we will use to determine the possible quantum jump transition is Bohr's atomic model
E = - 13.606 / n²
where ; n = integer
energy at ground state = 13.606 eV
The energy acquired by the electrons ( 12.5 eV ) is used to move the electron from its ground state to an excited state.
Therefore
ΔE = 13.606 * (1 / n₀² - 1 / n²) ---- ( 1 )
where n₀ = 1
Back to equation ( 1 )
ΔE = 13.606 (1 - 1/n²) -- ( 2 )
Resolving equation ( 2 )
1 / n² = 0.08129
n = 3.5 . Therefore the maximum integer = 3
Hence The collision between the electron and the hydrogen atom will undergo three ( 3 ) transition to reach the base state.
In Conclusion The possible quantum-jump transitions by which the excited atom emits a photon are :
Initial state Final state
3 ---> 2
3 ----> 1
2 ----> 1
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what happens to the speed of the
Skateboard/refrigerator when there is no longer a force being applied ?
Answer:
The speed stays constant after the force stops pushing.
Explanation:
Speed always stays constant when the force stops pushing it.
50 g of pieces of brass are heated to 200 ° C and then placed in the aluminum container of a 50 g calorimeter containing 160 g of water. What is the equilibrium temperature, if the temperature of the container and the water is initially 20 ° C?
Answer:
24.7°C
Explanation:
Heat lost by brass = heat gained by aluminum and water
-q = q
-mCΔT = mCΔT + mCΔT
-(50 g) (0.380 J/g/°C) (T − 200°C) = (50 g) (0.900 J/g/°C) (T − 20°C) + (160 g) (4.186 J/g/°C) (T − 20°C)
-(19 J/°C) (T − 200°C) = (45 J/°C) (T − 20°C) + (670 J/°C) (T − 20°C)
-(19 J/°C) (T − 200°C) = (715 J/°C) (T − 20°C)
-19 (T − 200°C) = 715 (T − 20°C)
-19T + 3800°C = 715T − 14300°C
18100°C = 734T
T = 24.7°C
If you wanted to find the area of the hot filament in a light bulb, you would have to know the temperature (determinable from the color of the light), the power input, the Stefan-Boltzmann constant, and what property of the filament
Answer:
To find out the area of the hot filament of a light bulb, you would need to know the temperature, the power input, the Stefan-Boltzmann constant and Emissivity of the Filament.
Explanation:
The emissive power of a light bulb can be given by the following formula:
E = σεAT⁴
where,
E = Power Input or Emissive Power
σ = Stefan-Boltzmann constant
ε = Emissivity
A = Area
T = Absolute Temperature
Therefore,
A = E/σεT⁴
So, to find out the area of the hot filament of a light bulb, you would need to know the temperature, the power input, the Stefan-Boltzmann constant and Emissivity of the Filament.
Parallel rays of monochromatic light with wavelength 582 nm illuminate two identical slits and produce an interference pattern on a screen that is 75.0 cm from the slits. The centers of the slits are 0.640 mm apart and the width of each slit is 0.434 mm. If the intensity at the center of the central maximum is 4.40×10^−4 W/m^2.
Required:
What is the intensity at a point on the screen that is 0.710 mm from the center of the central maximum?
Answer:
I = 0.56 10⁻⁴ W / m²
Explanation:
Double-slit interference is described by the expression
d sin θ = m λ
if we use trigonometry we can find the angle
tan θ= y / L
how the angles are small
tan θ = sin θ / cos θ = sin θ
sin θ = y / L
we substitute
d y / L = m λ
if we take into account that each slit also produces a diffraction phenomenon, the intensity distribution is the product of the intensity of the slits by the intensity of the diffraction process
I = I₀ cos² (d a) [(sin ba) / ba]²
a = π sin θ /λ
where the separation of the slits and b is the width of the slits
we substitute
I = I₀ [cos (d a)]² [sin ba /ba]²
a = π y / (L λ)
let's reduce the magnitudes to the SI system
λ = 582 nm = 582 10⁻⁹ m
L = 75.0 cm = 75.0 10⁻² m
d = 0.640 mm = 0.640 10⁻³ m
b = 0.434 mm = 0.434 10⁻³ m
Io = 4.40 10⁻⁴ W / m²
let's calculate for y = 0.710 mm = 0.710 10⁻³ m
a = π 0.710 10⁻³ / (75 10⁻² 582 10⁻⁹)
a = 5.11004 10³
I = 4.40 10⁻⁴ [cos (0.640 10⁻³ 5.11004 10³)]² (sin (0.434 10⁻³ 5.11004 10³) / (0.434 10⁻³ 5.11 10³)²
I = 4.40 10⁻⁴ cos² (3.2704) (sin 2.2178 / 2.2178)²
remember that the angles are in radians
I = 4.40 10⁻⁴ 0.9835 (0.79789 / 2.2178)²
I = 4.40 10⁻⁴ 0.9835 0.1294
I = 0.56 10⁻⁴ W / m²
An object–spring system undergoes simple harmonic motion. If the amplitude increases but the mass of the object is not changed, the total energy of the system:______.a. undergoes a sinusoidal change. b. decreases exponentially. c. decreases. d. doesn't change. e. increases.
Answer:
The correct answer is:
doesn't change (d)
Explanation:
The total energy in a system is the sum of Kinetic and Potential energies in a system, assuming that energy is not lost to an external procedure. Now, let us define what potential and kinetic energies are:
Potential Energy: this is energy at rest or stored energy
Kinetic Energy: this is energy in motion
In a simple harmonic motion of a mass-spring system, there is no dissipative force, hence the total energy is equal to the potential and kinetic energies. The total energy is not changed rather, it varies between potential and kinetic energies depending on the point at which the mass is. The kinetic energy is greatest at the point of lowest amplitude (highest velocity) and lowest at the point of greatest amplitude (lowest velocity), while potential energy is greatest at the point of highest amplitude (lowest velocity) and lowest at the point of smallest amplitude ( highest velocity). However, at every point, the sum of kinetic and potential energies equals total energy.
A car traveling initially at 8.0 m/s accelerates to a velocity of 14 m/s in 2.0s. What is the average acceleration of the car?
Answer:
3.0 m/s²
Explanation:
Given:
v₀ = 8.0 m/s
v = 14 m/s
t = 2.0 s
Find: a
v = at + v₀
14 m/s = a (2.0 s) + 8.0 m/s
a = 3.0 m/s²
Joe is hiking through the woods when he decides to stop and take in the view. He is particularly interested in three objects: a squirrel sitting on a rock next to him, a tree a few meters away, and a distant mountain. As Joe is taking in the view, he thinks back to what he learned in his physics class about how the human eye works.
Light enters the eye at the curved front surface of the cornea, passes through the lens, and then strikes the retina and fovea on the back of the eye. The cornea and lens together form a compond lens system. The large difference between the index of refraction of air and that of the aqueous humor behind the cornea is responsible for most of the bending of the light rays that enter the eye, but it is the lens that allows our eyes to focus. The ciliary muscles surrounding the lens can be expanded and contracted to change the curvature of the lens, which in turn changes the effective focal length of the cornea-lens system. This in turn changes the location of the image of any object in one's field of view. Images formed on the fovea appear in focus. Images formed between the lens and the fovea appear blurry, as do images formed behind the fovea. Therefore, to focus on some object, you adjust your ciliary muscles until the image of that object is located on the fovea.
A) Joe first focuses his attention (and his eyes) on the tree. The focal length of the cornea-lens system in his eye must be __________ the distance between the front and back of his eye.
a. greater than
b. less than
c. equal to
B) Joe's eyes are focused on the tree, so the squirrel and the mountain appear out of focus. This is because the image of the squirrel is formed ______ and the image of the mountain is formed _____.
a. between the lens and fovea / between the lens and fovea
b. between the lens and fovea / behind the fovea
c. behind the fovea / between the lens and fovea
d. behind the fovea / behind the fovea
C) Joe now shifts his focus from the tree to the squirrel. To do this, the ciliary muscles in his eyes must have _____ the curvature of the lens, resulting in a(n) _______ focal length for the cornea-lens system. Note that curvature is different from radius of curvature.
a. increased / increased
b. increased / decreased
c. decreased / increased
d. decreased / decreased
Answer:
A) correct answer is C, B) correct answer is b and C) The correct answer is b
Explanation:
In the exercises of geometric optics, the equation of the constructor tells us the location of the image.
1 / f = 1 / p + 1 / q
where f is the focal length of the cornea-crystalline system, p and q are the distances to the object and the image.
In this case, the distance to the image on the retina is constant, about 3 cm. Therefore depending on the distance to the object) p = the focal length must change
1 / q = 1 / f 1 / p
let's apply this expression to our case
A) indicates that the tree is at a medium distance
so that the image is formed on the retina THE SAME AS
correct answer is C
B) The squirrel is at a smaller distance (p ') than the tree (p), therefore if we substitute in the equation above we find that q must decrease. Consequently the image is in front of the retina
The mountain is very far, suppose in infinity, so the image is BEHIND THE RETINA
therefore the correct answer is b
C) The squirrel is very close so the curvature of the lens INCREASES, resulting in a DECREASE in the focal length
The correct answer is b
During an earthquake, the top of a building oscillates with an amplitude of 30cm at 1.5Hz.
Part A What is the magnitude of the maximum displacement from the equilibrium of the top of the building? (in cm)
Part B What is the maximum velocity of the top of the building?(in cm/s)
Part C What is the maximum acceleration of the top of the building?(in cm/s^2
A.30cm
B.282.7cm/s
C.26655cm/s²
Explanation:
A. Maximum displacement= Amplitude= 0.3m
B.mum velocity=
2πAf= 2π x 1.5x30 =282.7cm/s
C. Maximum acceleration
= ( angular velocity)² A= (2πf)² A
=( 2 x 3.142 x 1.5)² x 30
2665.5cm/s²
how high off the ground is a book that has 120 J of potential energy and a 4-kg mass ?
Answer:
3 m
Explanation:
PE = mgh
120 J = (4 kg) (10 m/s²) h
h = 3 m
The book is 3m high from the ground.
What is potential energy?The energy by virtue of its position is called the potential energy.
PE = mgh
where, g = 9.81 m/s²
Given is the mass of book m =4kg and the potential energy P.E = 120J, then the height is
120 J = (4 kg) (10 m/s²) h
h = 3 m
Thus, the book is 3m high from the ground.
Learn more about potential energy.
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Water flows through a valve with inlet and outlet velocities of 3 m/s. If the loss coefficient of the valve is 2.0, and the specific weight of water is 9800 N/m3, the pressure drop across the valve is most nearly:
Answer:
The value is [tex]\delta P = 9000 \ Pa[/tex]
Explanation:
From the question we are told that
The inlet and outlet velocity is [tex]v = 3 \ m/s[/tex]
The loss coefficient is [tex]k = 2[/tex]
Th specific weight of water is [tex]w = 9800 \ N/m^3[/tex]
Generally the pressure drop across the valve is mathematically represented as
[tex]\delta P = \frac{1}{2} * k * \rho * v^2[/tex]
Here [tex]\rho[/tex] is the density which is mathematically represented as
[tex]\rho = \frac{w}{g}[/tex]
=> [tex]\rho = \frac{9800}{9.8}[/tex]
=> [tex]\rho = 1000 \ kg/m^3[/tex]
So
[tex]\delta P = \frac{1}{2} * 2* 1000 * 3^2[/tex]
[tex]\delta P = 9000 \ Pa[/tex]