Answer:
2.04 minutes
Explanation:
He travels the first mile at 50 mph so:
[tex]60/50=1.2[/tex]
so it takes 1.2 minutes to travel each mile when going 50 miles per hour
and for the second mile he travels at 71 mph so:
[tex]60/71=0.84[/tex] (this answer is rounded)
so it takes him 0.84 minutes to travels each mile while going 71 mph.
If you ad them together his total times while biking two miles was 2.04 minutes.
Which event took place during Copernican revolution, When most people started to believe in a heliocentric model of the solar system
Answer:
Copernicus rediscovered Aristarchus’s heliocentric model
Explanation:
determine the weight in newtons of a woman whose weight in pounds is 125. also, find her mass in slugs and in kilograms. DEtermine your own weight in newtons
Answer:
124 just subtract only one
Explanation:
When an x-ray photon passes through matter it undergoes a process called:_________.
Answer:
when an x-ray passes trough matter, it undergoes a process called attenuation
In a thermal circulation what is happening at the surface of the warm column of air?
Answer:
Explanation: Thermals are created by the irregular heating of Earth's surface from solar radiation, and are an example of convection, specifically atmospheric convection.
At this point, air is converging on low pressure and rising air forms clouds.
Compare and contrast the inner and outer planets. (Must be in complete sentences) (At least 5 sentences).
To contrast inner and outer planets we will start with the climate of the planets and then move on to there lighting. To start the planets closet to the sun, mercury, venus, earth and mars, are all hot compared to the further one, jupiter, saturn, uranus, neptune. This distance also makes the farthe away planets darker than the ones closer. Now to compare all the planets vary from either gass or solid, rocky or icy. All of them spin around the sun and all have objects spinning around them, moons.
A vector is parallel to the y axis, what is it x component?
Answer:
Explanation:
A vector is parallel to the y axis .
Let its magnitude be A . So the vector can be represented as A j .
where i and j are unit vectors in x and y axis direction .
The x component of A j will be dot product of A j with i
The x component of A j = A j . i
= A x 0 [ Since j . i = 0 ]
= 0
When it comes to how ray lines are drawn, what makes the convex lens and concave mirror similar to each other?
Answer:
Convex lens and convex mirrors are similar that
1. They have the same image characteristics at various object positions
2. They possess a positive focal length
3. Both their ray lines converge to a particular focal point
Convex lens and concave mirror have certain similarities that are explained below.
The shape of concave mirror is spherical.
Convex lens is the combination of two concave mirrors.
When the ray lines are drawn at the convex lens, then the coverage of the rays leads parallel to its principal axis.
When the ray lines are drawn at the concave mirror, then the coverage of the rays leads parallel to its focal point.
The focal length of concave mirror and convex lens is positive.
Concave mirror and convex lens both project the real and inverted image of the object.
For more details, follow the link given below.
https://brainly.com/question/14295029.
The force on an object is F⃗ =−17j⃗ . For the vector v⃗ =2i⃗ +3j⃗ , find: (a) The component of F⃗ parallel to v⃗
Answer:
(a) [tex]\vec F_{\parallel} = -\frac{102}{13}\,i-\frac{103}{13}\,j[/tex] , (b) [tex]\vec F_{\perp} = \frac{102}{13}\,i -\frac{68}{13}\,j[/tex], (c) [tex]W = -51[/tex]
Explanation:
The statement is incomplete:
The force on an object is [tex]\vec F = -17\,j[/tex]. For the vector [tex]\vec v = 2\,i +3\,j[/tex]. Find: (a) The component of [tex]\vec F[/tex] parallel to [tex]\vec v[/tex], (b) The component of [tex]\vec F[/tex] perpendicular to [tex]\vec v[/tex], and (c) The work [tex]W[/tex], done by force [tex]\vec F[/tex] through displacement [tex]\vec v[/tex].
(a) The component of [tex]\vec F[/tex] parallel to [tex]\vec v[/tex] is determined by the following expression:
[tex]\vec F_{\parallel} = (\vec F \bullet \hat {v} )\cdot \hat{v}[/tex]
Where [tex]\hat{v}[/tex] is the unit vector of [tex]\vec v[/tex], which is determined by the following expression:
[tex]\hat{v} = \frac{\vec v}{\|\vec v \|}[/tex]
Where [tex]\|\vec v\|[/tex] is the norm of [tex]\vec v[/tex], whose value can be found by Pythagorean Theorem.
Then, if [tex]\vec F = -17\,j[/tex] and [tex]\vec v = 2\,i +3\,j[/tex], then:
[tex]\|\vec v\| =\sqrt{2^{2}+3^{3}}[/tex]
[tex]\|\vec v\|=\sqrt{13}[/tex]
[tex]\hat{v} = \frac{1}{\sqrt{13}} \cdot(2\,i + 3\,j)[/tex]
[tex]\hat{v} = \frac{2}{\sqrt{13}}\,i+ \frac{3}{\sqrt{13}}\,j[/tex]
[tex]\vec F \bullet \hat{v} = (0)\cdot \left(\frac{2}{\sqrt{13}} \right)+(-17)\cdot \left(\frac{3}{\sqrt{13}} \right)[/tex]
[tex]\vec F \bullet \hat{v} = -\frac{51}{\sqrt{13}}[/tex]
[tex]\vec F_{\parallel} = \left(-\frac{51}{\sqrt{13}} \right)\cdot \left(\frac{2}{\sqrt{13}}\,i+\frac{3}{\sqrt{13}}\,j \right)[/tex]
[tex]\vec F_{\parallel} = -\frac{102}{13}\,i-\frac{153}{13}\,j[/tex]
(b) Parallel and perpendicular components are orthogonal to each other and the perpendicular component can be found by using the following vectorial subtraction:
[tex]\vec F_{\perp} = \vec F - \vec F_{\parallel}[/tex]
Given that [tex]\vec F = -17\,j[/tex] and [tex]\vec F_{\parallel} = -\frac{102}{13}\,i-\frac{153}{13}\,j[/tex], the component of [tex]\vec F[/tex] perpendicular to [tex]\vec v[/tex] is:
[tex]\vec F_{\perp} = -17\,j -\left(-\frac{102}{13}\,i-\frac{153}{13}\,j \right)[/tex]
[tex]\vec F_{\perp} = \frac{102}{13}\,i + \left(\frac{153}{13}-17 \right)\,j[/tex]
[tex]\vec F_{\perp} = \frac{102}{13}\,i -\frac{68}{13}\,j[/tex]
(c) The work done by [tex]\vec F[/tex] through displacement [tex]\vec v[/tex] is:
[tex]W = \vec F \bullet \vec v[/tex]
[tex]W = (0)\cdot (2)+(-17)\cdot (3)[/tex]
[tex]W = -51[/tex]
A steel tank of weight 600 lb is to be accelerated straight upward at a rate of 1.5 ft/sec2. Knowing the magnitude of the force P is 525 lb, determine the values of the angle a and the required magnitude of the vertical force, F.
Answer:
a) the values of the angle α is 45.5°
b) the required magnitude of the vertical force, F is 41 lb
Explanation:
Applying the free equilibrium equation along x-direction
from the diagram
we say
∑Fₓ = 0
Pcosα - 425cos30° = 0
525cosα - 368.06 = 0
cosα = 368.06/525
cosα = 0.701
α = cos⁻¹ (0.701)
α = 45.5°
Also Applying the force equation of motion along y-direction
∑Fₓ = ma
Psinα + F + 425sin30° - 600 = (600/32.2)(1.5)
525sin45.5° + F + 212.5 - 600 = 27.95
374.46 + F + 212.5 - 600 = 27.95
F - 13.04 = 27.95
F = 27.95 + 13.04
F = 40.99 ≈ 41 lb
the process of _ is when tow atoms combine to form a larger atom, releasing energy
Answer:Nuclear fusion is the process by which two or more atomic nuclei join together, or “fuse,” to form a single heavier nucleus. During this process, matter is not conserved because some of the mass of the fusing nuclei is converted to energy, which is released.
Explanation:
Atoms of different elements can combine to make new substances. A molecule is formed when two or more atoms join together chemically. If atoms combine that are of two or more different elements, we call that a compound. ... When two hydrogen atoms combine with one oxygen atom, it becomes the compound water.
Answer:
nuclear fusion
Explanation:
Name at 2 areas of physics that make video games possible
Answer:
projectiles
electromagnetic
Answer:
Explanation:
física cuántica y Quantum Moves
About how many times greater is the density of a neutron star compared to a white dwarf?
Answer:
Explanation:
over a million times
answers If the motor is to accelerate the elevator car upward at 1.8 m/s2, how much torque must it generate
Answer:
Hello your question is incomplete attached is the missing diagram and solution
One elevator arrangement includes the passenger car, a counterweight, and two large pulleys, as shown in (Figure 1). Each pulley has a radius of 1.2 m and a moment of inertia of 410 kg⋅m2. The top pulley is driven by a motor. The elevator car plus passengers has a mass of 3000 kg, and the counterweight has a mass of 2600 kg.
a) If the motor is to accelerate the elevator car upward at 1.8 m/s2, how much torque must it generate? Express your answer to two significant figures and include appropriate units.
Answer : 6030 N.m ≈ 6000 N.m
Explanation:
To determine how much torque the motor accelerating at 1.8 m/s^s will generate we will have to determine T1 ( tension generated for upward acceleration in the rope ) and Tg ( tension generated in the rope when there is a counterweight accelerating downwards)
Torque in the pulley (T2) = (T1 - Tg ) r
torque generated by motor = T1 + T2 = 1230 + 4800 = 6030 N.m to two significant figures = 6000 N.m
r = 1.2
a = 1.8
attached below is the remaining part of the solution
Question No 1 Find the voltage drop across 24 ohm resistor and current flowing through 22 ohm resistor in the given circuit as shown in figure.
Answer:
8.25 V
Explanation:
We can ignore the 22Ω and 122Ω resistors at the bottom. Since there's a short across those bottom nodes, any current will go through the short, and none through those two resistors.
The 2Ω resistor and the 44Ω resistor are in parallel. The equivalent resistance is:
1 / (1 / (2Ω) + 1 / (44Ω)) = 1.913Ω
This resistance is in series with the 12Ω resistor. The equivalent resistance is:
1.913Ω + 12Ω = 13.913Ω
This resistance is in parallel with the 24Ω resistor. The equivalent resistance is:
1 / (1 / (13.913Ω) + 1 / (24Ω)) = 8.807Ω
Finally, this resistance is in series with the 4Ω resistor. The equivalent resistance of the circuit is:
8.807Ω + 4Ω = 12.807Ω
The current through the battery is:
12 V / 12.807Ω = 0.937 A
The voltage drop across the 4Ω resistor is:
(0.937 A) (4Ω) = 3.75 V
So the voltage between the bottom nodes and the top nodes is:
12 V − 3.75 V = 8.25 V
According to Einstein, increasing the brightness (or intensity) of a beam of light without changing its color will increase (circle all that apply):
The question is incomplete,so the complete question is as follows:
According to Einstein, increasing the brightness (or intensity) of a beam of light without changing its color will increase (circle all that apply):
A) the number of photons per second traveling in the beam.
B) the energy of each photon.
C) the speed of the photons.
D) the frequency of the light.
E) the wavelength of the photons
Answer:
A)
Explanation:
According to Einstein, an increase in the intensity or brightness of light beam will increase the number of photons over a given time interval.
It means that the energy emitted will depend on the energy of individual photon rather than the intensity of the incoming light.
Hence, the correct option is "A)"
What is the wavelength of the waves you create in a swimming pool if you splash your hand at a rate of 2.00 Hz and the waves propagate at 0.800 m/s
Answer:
The wavelength of the waves created in the swimming pool is 0.4 m
Explanation:
Given;
frequency of the wave, f = 2 Hz
velocity of the wave, v = 0.8 m/s
The wavelength of the wave is given by;
λ = v / f
where;
λ is the wavelength
f is the frequency
v is the wavelength
λ = 0.8 / 2
λ = 0.4 m
Therefore, the wavelength of the waves created in the swimming pool is 0.4 m
A uniform seesaw is balanced at its center of mass, as seen below. The smaller boy on the right has a mass of 40.0 kg. What is the mass of his friend is (A) 40 kg (B) 20 kg (C) 80 kg (D) Cannot be determined
Answer:
C. 80kgExplanation:
The question lacks the appropriate diagram. Find the diagram attached below:
Let the mass of his friend be M.
Using the principle of moment which states that the sum of clockwise moment is equal to the sum of its anticlockwise moment to solve the problem,.
Since Moment = Force * perpendicular distance.
The smaller boy will move in the clockwise direction and his friend will move in the anti clockwise direction.
Clockwise moment = 40 * 4 = 160kgm
anticlockwise moment = M * 2 = 2Mkgm
Equating both moments to get the mass M of his friend
160 = 2M
Divide both sides by 2
2M/2 = 160/2
M = 80kg
Hence the mass of his friend that will keep the seesaw balanced horizontally is 80kg.
Solve for x
–30 = 5(x + 1)
Answer:
-30=5(x+1) is -7
Explanation:
distribute flip subtract 5 from both sides divide both sides by 5
What is the maximum power that can be delivered by a 1.4-cm-diameter laser beam propagating through air
Complete Question
The maximum electric field strength in air is 4.0 MV/m. Stronger electric fields ionize the air and create a spark. What is the maximum power that can be delivered by a 1.4-cm-diameter laser beam propagating through air
Answer:
The value is [tex]P = 3.270960 *10^{6} \ W[/tex]
Explanation:
From the question we are told that
The electric field strength is [tex]E = 4.0 \ M \ V/m = 4.0 *10^6 \ V/m[/tex]
The diameter is [tex]d = 1.4 \ cm = 0.014 \ m[/tex]
Generally the radius is mathematically represented as
[tex]r = \frac{d}{2}[/tex]
=> [tex]r = \frac{0.014}{2}[/tex]
=> [tex]r = 0.007 \ m[/tex]
Generally the cross-sectional area is mathematically represented as
[tex]A = \pi r^2[/tex]
[tex]A = 3.142 * (0.007)^2[/tex]
[tex]A = 0.000154 \ m^2[/tex]
Generally the maximum power that can be delivered is mathematically represented as
[tex]P = \frac{c * \epsilon_o * E^2 * A }{2}[/tex]
Here c is the speed of light with value [tex]c = 3.0*10^{8} \ m/s[/tex]
[tex]\epsilon_o[/tex] is the permittivity of free space with value [tex]\epsilon_o = 8.85 *10^{-12} \ m^{-3} \cdot kg^{-1}\cdot s^4 \cdot A^2[/tex]
[tex]P = \frac{3,0*10^8 * 8.85*10^{-12} * (4 *10^6)^2 * 0.00154}{ 2}[/tex]
[tex]P = 3.270960 *10^{6} \ W[/tex]
Skater A skates toward Skater B and gently pushes Skater B away. If the skaters are in a closed system, which statement is correct about the total momentum of the system? A. Total momentum may increase or decrease depending on the duration of the collision. B. Total momentum remains the same. C. Total momentum increases. D. Total momentum decreases.
Answer:
option B is correct
Explanation:
according to law of conservation of momentum the total momentum in a closed system remains constant before and after collision
If the skaters are in a closed system the total momentum remains the same.
In a closed system the total momentum is always conserved.
By applying the principle of conservation of linear momentum, the total momentum before the push of skater A, will be equal to the total momentum after the push.
The equation is given as;
Initial momentum = final momentum
[tex]m_au_a + m_bu_b = m_av_a + m_bv_b[/tex]
where;
u and v represents the initial and final velocity of both skaters.Thus, we can conclude that if the skaters are in a closed system the total momentum remains the same.
Learn more here: https://brainly.com/question/7538238
If two identical blocks are glued together and pulled with twice the original force, what will their acceleration be
Answer:
The acceleration will be a
Explanation:
Using F = ma
But we are given that F2= 2F1 and
m2= 2m1
So
a2= F2/m2= F1/m1
and
F1/m1=a
Work: If the force on an object is in the negative direction, the work it does on the object must be
Answer:
The work must be negative or positive depending on direction of motion of the object
Explanation:
This is because
W= force x distance
And = F x S cosစ
And this is positive when
Theta is less than π/2 and negative when theta is less than or equal to π/2
If a force acts in a specific direction on a thing, the work it puts on it can be positive or negative, regardless of the direction the object moves.
Define force.A force is indeed an influence which can alter an angular velocity. An object can alter its velocity, or speed, as a result of a force. Naturally, force can be characterized as a push or just a pull.
If a force acts in a specific direction on a thing, the work it puts on it can be positive or negative, regardless of the direction the object moves.
Find out more information about force here:
https://brainly.com/question/26115859?referrer=searchResults
How much energy is stored in the capacitor before the dielectric is inserted?Express your answer in joules.
Answer:
0.004394Joules
Explanation:
The question is incomplete. Find the complete question in the attachment below;
Energy stored in a capacitor = 1/2CV² where;
C is the capacitance of the capacitor
V is the potential difference across the plates
Given parameters
C = 13.0μF = 13 * 10⁻⁶F
V = 26.0V
Required
Energy stored in the capacitor
Substituting the values into the equation given;
E = 1/2 * 13 * 10⁻⁶ * 26²
E = 1/2 * 13 * 10⁻⁶ * 676
E = 1/2* 8788 * 10⁻⁶
E = 4394 * 10⁻⁶
Hence the Energy stored in the capacitor in Joules is 0.004394Joules
Re-arrange the equation
x = vit + 1/2at2 v2f = vi2 + 2ax vf = vi + at x = 1/2(vi + vf)delta t
1. A car in front of the school goes from rest to 27 ms in 3.0 seconds. What is its acceleration (assuming it is constant)?
2. A rocket starts from rest and accelerates at a uniform rate of 190 m/s^2 for 2.4 seconds. What is its final velocity?
3. A car has a velocity of 15 m/s. It then accelerates at a uniform rate of 3.5 m/s^2 for the next 5.0 seconds. What distance does the car cover during this time?
4. What distance is required for a train to stop if its initial velocity is 23 m/s and its deceleration is 0.25 m/s^2? (Assume the train decelerates at a constant rate.
5. What distance will a car cover while uniformly accelerating from 12 m/s to 26 m/s in 14 seconds?
6. A person starts at rest and accelerates at a uniform rate of at 3.2 m/s^2 for 3.0 seconds. What distance does this person cover in that time?
7. What must be the acceleration of a train in order for it to stop from 12 m/s in a distance of 541 m? (Assume the train accelerates uniformly.)
Answer:
Explanation:
1) Acceleration is the change in velocity of a body with respect to time.
Acceleration a = vf - vi/t
vf is the final velocity
vi is the initial velocity.
t is the time taken
Since the body accelerates from rest, vi = 0m/s
a = 27-0/3
a = 27/3
a = 9m/s²
2) Given
u = 0m/s (accelerates from rest)
a = 190m/s²
t = 2.4seconds
v = ?
Using v = u+at
v = 0+190(2.4)
v = 190×2.4
v = 456m/s
The final velocity of the car is 456m/s
3) Given
u = 15m/s
a = 3.5m/s
t = 5seconds
Using the relationship
S = ut+1/2at²
S is the distance covered by the car.
S = 15(5)+1/2(3.5)×5²
S = 75+25×3.5/2
S = 75+43.75
S = 118.75m
4) Given
initial velocity u = 23m/s
Deceleration a = -0.25m/s²(negative acceleration)
Final velocity v = 0m/s
Using the relationship
V² = u²+2as
0² = 23²+2(-0.25)s
-23² = -0.5S
23² = 0.5S
S = 529/0.5
S = 1058m
The distance required for the train to stop is 1058m.
5) Given
initial velocity u = 12m/s
Final velocity v = 26m/s
time = 14sec
Acceleration a = v-u/t
a = 26-12/14
a= 14/14
a = 1m/s²
For Distance covered
v² = u²+2as
26² = 12²+2(1)S
676 = 144 +2S
2S = 676-144
2S = 532
S = 532/2
S = 266m
Distance that the car will cover is 266m
6) Given
Initial velocity u = 0m/s (person starts from rest)
acceleration a = 3.2m/s²
time t = 3.0s
To get the distance;
S = ut + 1/2at²
S = 0(3)+1/2(3.2)×3²
S = 0+1.6×9
S= 9×1.6
S = 14.4m
The distance that the person covered in 3.0s is 14.4m
7) initial velocity of train u = 12m/s
Distance covered S = 541m
Final velocity = 0m/s (on stopping)
acceleration a= ?
Acceleration will be negative since the train is coming to a stop (decelerating)
Using the formula v² = u²+2as
0² = 12² - 2a(541)
-12² = -1082a
144 = 1082a
a = 1082/144
a = 7.51m/s²
Hence the acceleration of a train in order for it to stop from 12 m/s in a distance of 541 m is 7.51m/s²
What is the magnitude of the electric force on the charge at the bottom left-hand vertex of the triangle due to the other two charges
Answer:
[tex]\frac{kq^{2} }{2a^2}[/tex]
Explanation:
The magnitude on the charge at the bottom-left corner due to the charge on the top vertex of the triangle will act along the +ve x-axis and the +ve y-axis.
From Coulomb's law the magnitude of the forces on the charge at the bottom-left corner, due to the charge on the top vertex of the triangle are [tex]\frac{kq^{2} }{a^2}[/tex]cos 60, and
The magnitude on the charge due to the charge at the bottom-right corner will only act in the -ve x-axis, since they repel each other (like charges repel). The magnitude is [tex]\frac{kq^{2} }{a^2}[/tex]
The angle made by the upper charge to the charge we're considering is 60° with the horizontal.
The total force on the charge along the x-axis is
[tex]F_{x}[/tex] = [tex]\frac{kq^{2} }{a^2}[/tex]cos 60 -
[tex]F_{x}[/tex] = [tex]\frac{kq^{2} }{2a^2}[/tex] - [tex]\frac{kq^{2} }{a^2}[/tex]
==> -[tex]\frac{kq^{2} }{2a^2}[/tex]
For the y-axis, we have
[tex]F_{y}[/tex] = [tex]\frac{kq^{2} }{a}[/tex]sin 60
[tex]F_{y}[/tex] = [tex]\frac{\sqrt{3}* kq^{2} }{2a^2}[/tex]
The resultant force is
[tex]|F| = \sqrt{F_{x}^{2}+ F_{y}^2 }[/tex]
The common factors between the two x-axis force, and the y-axis force is
[tex]\frac{kq^{2} }{2a^2}[/tex], we put this outside the square root (squaring this and square rooting will give us the initial value)
[tex]|F|[/tex] = [tex]\frac{kq^{2} }{2a^2}[/tex][tex]\sqrt{(\frac{1}{2})^2 + (\frac{\sqrt{3} }{2})^2 }[/tex]
[tex]|F|[/tex] = [tex]\frac{kq^{2} }{2a^2}[/tex][tex]\sqrt{\frac{1}{4} +\frac{3}{4} }[/tex]
==> [tex]\frac{kq^{2} }{2a^2}[/tex][tex]\sqrt{1}[/tex]
the magnitude of the electric force on the charge at the bottom left-hand vertex of the triangle due to the other two charges is
[tex]|F|[/tex] = [tex]\frac{kq^{2} }{2a^2}[/tex]
5. Haley throws her ball downward with speed v from height 2h. Simultaneously, Joe drops his ball from rest at height h. What should v be so that the two balls hit the ground at the same time
Answer:
We know that the second equation of motion is
S= ut + 1/2a²
And S is displacement and u is initial velocity
So in the case of Haley lets take downwards as positive Y-axis
S = 2h and
initial velocity = v
a = g (acceleration due to gravity = 9.8)
Substituting
2h = vt + 1/2gt²
And for Joe we take ownwards as positive Y-axis
S = h and
initial velocity = 0 (since the ball is dropped from rest)
a = g
h = 0x t + 1/2gt2²
t2= √ 2h/g
Now since both balls reach ground at same time: t1=t2
So
putting value of t2 in Hayley's equation:
2h= v(√2h/g) + 1/2 g( √2h/g)²
So v= √gh/2
If the radiant energy from the Sun comes in as a plane EM wave of intensity 1340 W/m2, calculate the peak values of E and B
Answer:
Given that
I = 1340 W/m²
µo = 4πx 10^-7 Tm/A
sc = 3 x 10^8 m/s
So to find the peak values of B we use
I = (c Bm²) / (2 µo)
1340 = (3 x 10^8 x Bm²) / (2 x 4πx 10^-7)
1340 = (3 x 10^8 x Bm²) / (25.12 x 10^-7)
(3 x 10^8 x Bm²) = 1340 x (25.12 x 10^-7)
(3 x 10^8 x Bm²) = 3.366 x 10^-3
Bm² = 3.366 x 10^-3 / 3 x 10^8
Bm² = 1.122 x 10^-11
Bm = 3.4 x 10^-6 T
Also to find the peak values of E we
use Em = c x Bm
Em = (3 x 10^8) (3.4 x 10^-6)
Em = 1.005 N/C
Kendra drove 300 km in 2 hours. Henry drove the same 300 km in 3 hours. If
Kendra and Henry had the same average speed for their trips, what must be
true?
a. Kendra must have stopped for one hour during her trip
b. henry must have stopped for one hour during his trip
c. kendra must have had a lower velocity than henry
d. henry must have had a lower velocity then kendra
Answer:
b. henry must have stopped for one hour during his trip
A jogger runs 4 km in 0.4 hr, then 8 km in 0.8 hr. What is the average speed of the jogger?
Answer:
2km
Explanation:
A beam of gamma rays is incident on a block of lead. The intensity of gamma rays passing through a uniform medium varies with depth x, in a manner given by the expression I(x) = 1, e-ux Here, I, is the intensity of the radiation at the surface of the material (at x = 0) and u is called the linear absorption coefficient. A) Find an expression for the thickness of material that would absorb half of the gamma rays. B) Find an expression for the thickness of material that would reduce the radiation intensity to a fraction of the initial intensity.
Answer:
A. x = -㏑(1/2)/μ B. x = -㏑(I/I₀)/μ
Explanation:
A. Since the intensity I = I₀exp(-μx) where I₀ = intensity at x = 0.
When I = I₀/2,
I = I₀exp(-μx)
I₀/2 = I₀exp(-μx)
dividing through by I₀, we have
1/2 = exp(-μx)
taking natural logarithm of both sides, we have
㏑(1/2) = ㏑[exp(-μx)]
㏑(1/2) = -μx
dividing both sides by -μ
x = -㏑(1/2)/μ
where x is the thickness of the material that would absorb half of the gamma rays
B. Since the intensity I = I₀exp(-μx) at thickness x, where I₀ = intensity at x = 0
I = I₀exp(-μx)
dividing through by I₀
I/I₀ = exp(-μx)
taking natural logarithm of both sides, we have
㏑(I/I₀) = ㏑exp(-μx)
㏑(I/I₀) = -μx
dividing both sides by -μ
x = -㏑(I/I₀)/μ
where x is the thickness of the material that would reduce the radiation intensity to a fraction of the initial intensity.