Answer:
201.8 days
Explanation:
The activity of a radioactive sample as a function of times is :
[tex]$R=R_0e^{\frac{0.693t}{T_{1/2}}}$[/tex]
Here, [tex]$R_0$[/tex] = the initial activity
[tex]$T_{1/2}$[/tex] = half life
t = elapsed time
Now rearranging the equation for time, t, we get:
[tex]$\frac{R}{R_0}=e^{-\frac{0.693t}{T_{1/2}}}$[/tex]
[tex]$\ln\left(\frac{R}{R_0}\right)=-\frac{0.693t}{T_{1/2}}$[/tex]
[tex]$t=\frac{-\ln\left(\frac{R}{R_0}\right)T_{1/2}}{0.693}$[/tex]
[tex]$t=\frac{-\ln\left(\frac{25}{350}\right)\times 53}{0.693}$[/tex]
= 201.8 days
Therefore, the required time is 201.8 days
What is the net force on a skydiver falling with a constant velocity of 0 m/s downward?
Which of the following is a problem with the estimated age of the universe?
There are stars in our galaxy that appear to be over 15 billion years old.
The universe is shrinking, which makes it is impossible to tell how old it is.
There should be more supergiants if the universe is really about ten billion years old.
There are planets in other galaxies that are less than five billion years old.
Answer:
There are stars in our galaxy that appear to be over 15 billion years old.
Explanation:
The age of the universe is the time past since the big ban event as based on observations of the early state of the universe. The comic problem with the universe is that it's estimated to be older since the time of the big bang. It also represents a contrast with objects in the galaxies such as stars, planets that could not have been present.how hot can the desert get
Answer:
134 f
Explanation:
The hottest temperature ever reliably measured in a desert was 134 degrees F, in Death Valley of the Mojave Desert in 1913.
Temperature. During the day, desert temperatures rise to an average of 38°C (a little over 100°F). At night, desert temperatures fall to an average of -3.9°C (about 25°F). At night, desert temperatures fall to an average of -3.9 degrees celsius (about 25 degrees fahrenheit).
Desert surfaces receive a little more than twice the solar radiation received by humid regions and lose almost twice as much heat at night. Many mean annual temperatures range from 20-25 degrees Celsius. The extreme maximum ranges from 43.5-49 degrees Celsius. Minimum temperatures sometimes drop to -18 degrees Celsius.
HURRY ILL GIVE 15 POINTS
Carla draws two circuit diagrams that connect the same components in different ways as shown which statement about the circuit is correct?
Circuit A is correct
Magnesium hydroxide is a common ___?
Answer:
Hello There!!
Explanation:
The answer is=> It is a common component of antacids.
hope this helps,have a great day!!
~Pinky~
40 points! Will give brainliest!
Which of the following describes an advantage of AC electricity over DC electricity?
A) AC is found in most low voltage operations.
B) AC is provided as strong, short bursts of electricity.
C) AC can be transported over long distances.
D) AC can be used is small electronic devices.
Which is one way to determine whether a reaction was a chemical reaction or a nuclear reaction?
Answer:
Check how much energy was released during the reaction or check for a change in total mass
Write a method which prevents ice from melting quickly.
Answer:
blocks of ice are usually covered with cloth or sawdust while being stored
How does a generator use the effect you noticed in the pickup coil to generate electrical energy? What energy transformations are taking place? Why does a generator make alternating current? What change would have to be made to make direct current?
Answer:
Movement of Electrons in opposite direction of the rotation of the pickup coil leads to the direction of Electrical energy ( Alternating current ).
Explanation:
For a Generator to generate electricity, Electrons that is found in the rotating coil of the Generator will experience some sort of force that makes them to start moving in a direction that is perpendicular to the direction of the rotating/pickup coil found in the Generator.
The conversion of mechanical energy (Rotation of the pickup coil ) to electrical energy takes place in the Generator
The generator makes an alternating current because electrons move in opposite direction of the rotating coil
In other to generate a Direct current using a generator we have to replace the slip rings with commutator.
A student must determine how the mass of a block affects the period of oscillation when the block is attached to a vertical spring. The value of the spring constant is known. The student writes the following experimental procedure.
1. Use an electronic balance to measure the mass of the block.
2. Attach the block to the vertical spring.
3. Displace the block from the system's equilibrium position to a new vertical position.
4. Release the block from rest.
5. Use a meterstick to measure the vertical displacement of the center of mass of the block from the system's equilibrium position to its maximum vertical position above the equilibrium position.
6. Use a stopwatch to measure the time it takes for the system to make ten complete oscillations.
7. Repeat the experiment for different vertical displacements and block masses.
Which of the following steps of the procedure should the student revise to make the determination? Justify your selection.
a. Step 3, because the student must specify whether the new vertical position should be above or below the system's equilibrium position.
b. Step 5, because the meterstick should be used to measure total displacement of the system from its lowest vertical position to its highest vertical position.
c. Step 6, because the stopwatch should be used only to measure the time it takes for the system to make 1 complete oscillation.
d. Step 7, because the experiment should not be repeated for different vertical displacements and block masses.
Answer:
the step that the student should change is step 7
Explanation:
The movement of the spring with block is a simple harmonic type movement, so the procedure proposed by the student is correct, but we must take some care.
Step 3 is important since each movement will be started with similar conditions, also if any displacement is very large we can get out of the linear approximation of Hooke's law, for which we need to know the equilibrium point, since from this point displacements will be measured.
Step 6 should be changed to measure various oscillations to find the average period and thus decrease the error in the time reading.
Step 7 is wrong since the objective of the experiment is to analyze the effect of different masses in the period of oscillation and this step prevents this objective from being carried out.
In conclusion, the step that the student should change is step 7
The step that should be revised to make the determination is c. Step 6, because the stopwatch should be used only to measure the time it takes for the system to make 1 complete oscillation.
Why should step 6 be revised?The student is trying to find the effect of the mass of the block on the period of oscillation in different vertical displacements.
The best way to do this is to measure the time taken per oscillation as this would show a much clearer picture to find the effect of the mass on the oscillation. Timing 10 oscillations will yield incorrect results.
In conclusion, option C is correct.
Find out more on measuring the effect of mass on oscillation at https://brainly.com/question/14745507.
A loudspeaker, mounted on a tall pole, is engineered to emit 75% of its sound energy into the forward hemisphere, 25% toward the back. You measure an 85 dB sound intensity level when standing 3.5 m in front of and 2.5 m below the speaker. What is the speaker’s power output?
Answer:
"0.049 W" is the correct answer.
Explanation:
According to the given question,
[tex]r = \sqrt{(3.5)^2+(2.5)^2}[/tex]
[tex]=\sqrt{8.5}[/tex]
[tex]SL=85[/tex]
As we know,
⇒ [tex]SL=10 \ log(\frac{I}{I_o} )[/tex]
[tex]85=10 \ log(\frac{I}{10^{-12}} )[/tex]
[tex]I=3.162\times 1^{-4} \ W/m^2[/tex]
Now,
⇒ [tex]P_{front} = I(2\pi r^2)[/tex]
[tex]=(3.162\times 10^{-4})(2\pi\times 18.5)[/tex]
[tex]=0.0368 \ W[/tex]
[tex]=0.75 \ P[/tex]
or,
[tex]=0.049 \ W[/tex]
A flying stationary kite is acted on by a force of 9.8 N downward. The wind exerts a force of 45 N at an angle of 50.0 degrees above the horizontal. Find the force that the string exerts on the kite.
Answer:
38 N, 40.0° below the horizontal
Explanation:
Force exerted by an object equals mass times acceleration of that object: F = m ⨉ a. To use this formula, you need to use SI units: Newtons for force, kilograms for mass, and meters per second squared for acceleration.
What is the definition of Heat Transfer
Answer:
Heat transfer is an engineering discipline that concerns the generation, use, conversion, and exchange of heat (thermal energy) between physical systems.
Explanation:
Answer:
Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, thermal convection, thermal radiation, and transfer of energy by phase changes.
Explanation:
hope that helps
The total resistance of a series circuit is 15.0 ohms what is the second resistance of the first resistance is 10.0 ohms?
A. less than 5.0 ohms
B. 5.0 ohms
C. 15 ohms
D. 25 ohms
Magnets on the tracks
How can levitating trains support the claim that magnetic fields exist between objects exerting magnetic force on each other even when there is no physical contact?
Answer:
Explanation: They levitate sort of because when to opposite forces of magnets cant go together they repelQ: Winding roads and sharp curves are inherently dangerous
because -
A- You can't see far ahead
B- The speed limit is so slow
C- There may be other vehicles traveling in the
opposite direction
D- You may struggle to stay at the same speed
Answer:
A) you can't see far ahead
D. You may struggle to stay at the same speed.
Winding roads and sharp curves are dangerous because of centrifugal forces while taking curves, whose classic formula is described below:
[tex]F = m\cdot \frac{v^{2}}{r}[/tex] (1)
Where:
[tex]F[/tex] - Centrifugal force, in newtons.[tex]v[/tex] - Speed, in meters per second.[tex]r[/tex] - Radius of curvature, in meters per second.Sharps curves are characterized by low radii of curvature. Given that centrifugal force is inversely proportional to the square radius of curvature and it is opposed to friction force between tires and pavement, if centrifugal force is higher than maximum static friction force, then a car accident could if driver does not decelerate.
Therefore, correct choice is D.
We kindly invite to see this question on centrifugal forces: https://brainly.com/question/545816
At what rate is thermal energy being generated in the 2R-resistor when ε = 12 V and R = 3.0 Ω?
Answer:
6 W
Explanation:
From the given information:
The resistance in Parallel for 2R is:
[tex]R_p = \dfrac{2R\times 2R}{2R+2R} \\ \\ R_p= R[/tex]
The equivalent resistance:
[tex]R_{eq} = R_p + R = 2R[/tex]
[tex]R_{eq} = 2(3)[/tex]
[tex]R_{eq} = 6 \ \ ohms[/tex]
The current through the circuit in R is:
[tex]= \dfrac{12}{R+R} \\ \\ = \dfrac{12}{2\times 3} \\ \\ = 2 A[/tex]
The current through the circuit in 2R is:
[tex]I_2R = (2A) \times \dfrac{2R}{2R+2R}[/tex]
[tex]I_2R = 2A \times \dfrac{1}{2} \\ \\ I_2R = 1A[/tex]
Finally, the thermal energy:
[tex]P_{2R} = (1)^2 (2R)[/tex]
[tex]P_{2R} = (1)^2 (2\times 3)[/tex]
[tex]P_{2R} = 6W[/tex]
A bat emits a sound at a frequency of 30.0 kHz as it approaches a wall. The bat detects beats such that the frequency of the echo is 900 Hz higher than the frequency the bat is emitting. The speed of sound in air is 340 m/s at emits a sound at a frequency of 30.0 kHz
(a) What is the speed of the bat?
(b) What is the wavelength of the sound that the bat hears15?
Answer:
a) the speed of the bat is 5.02 m/s
b) the wavelength of the sound that the bat hears is 0.011 m
Explanation:
Given the data in the question;
Frequency of sound emitted by a bat f = 30.0 kHz = 30000 Hz
detected frequency by the bat δf = 900 Hz
speed of sound in air c = 340 m/s
Let speed of sound and speed of bat be c and [tex]v_s[/tex] respectively;
Now, frequency of the sound that is coming from the bat towards the wall due to DROPPLER EFFET will be;
f₁ = ( c / ( c - [tex]v_s[/tex] ) )f ----- let this be equ 1
Also, frequency does not change after deflection. The bat becomes an observer as the dropper is shifted because the reflected sound wave is coming towards it;
Hence, Doppler shifted frequency will be;
f₂ = ( (c + [tex]v_s[/tex] ) / c )f₁
from equ 1, f₁ = ( c / ( c - [tex]v_s[/tex] ) )f, so we substitute
f₂ = ( (c + [tex]v_s[/tex] ) / c ) × ( c / ( c - [tex]v_s[/tex] ) )f
f₂ = ( (c + [tex]v_s[/tex] ) / ( c - [tex]v_s[/tex] ) )f
∴ beat frequency will be;
δf = f₂ - f = ( (c + [tex]v_s[/tex] ) / ( c - [tex]v_s[/tex] ) )f - f
δf = ( 2[tex]v_s[/tex] / c - [tex]v_s[/tex] )f
δf = ( 2[tex]v_s[/tex] / c - [tex]v_s[/tex] )f
2f/δf = c - [tex]v_s[/tex] / [tex]v_s[/tex]
2f/δf = c/[tex]v_s[/tex] - [tex]v_s[/tex] / [tex]v_s[/tex]
2f/δf = c/[tex]v_s[/tex] - 1
c/[tex]v_s[/tex] = 2f/δf + 1
[tex]v_s[/tex] = c / (2f/δf + 1)
now, we substitute in our values;
[tex]v_s[/tex] = 340 / ((2×30000 / 900 ) + 1)
[tex]v_s[/tex] = 340 / (66.6666 + 1)
[tex]v_s[/tex] = 340 / 67.6666
[tex]v_s[/tex] = 5.02 m/s
Therefore, the speed of the bat is 5.02 m/s
b) the wavelength of the sound that the bat hears
frequency of reflected wave is;
f₂ = f + δf = 30000 + 900 = 30900 Hz
λ₂ = c / f₂
we substitute
λ₂ = 340 / 30900
λ₂ = 0.011 m
Therefore, the wavelength of the sound that the bat hears is 0.011 m
what is the focalength of the combination of two thin renses of power -5D and -2D placeci in contact with each other?
Answer:
f = - 0.143 m = - 14.3 cm
Explanation:
First, we will calculate the power of the combination of lenses:
P = P₁ + P₂
where,
P = Power of Combination = ?
P₁ = Power of first lens = - 5D
P₂ = Power of second lens = - 2D
Therefore,
P = - 5D - 2D
P = - 7D
Now, the focal length can be given as:
[tex]f = \frac{1}{P} \\\\f = \frac{1}{-\ 7\ D} \\\\[/tex]
f = - 0.143 m = - 14.3 cm
Negative focal length indicates that combination will act as diverging lens.
A physics professor demonstrates the Doppler effect by tying a 900 Hz sound generator to a 1.0- m -long rope and whirling it around her head in a horizontal circle at 100 rpm .
1. What is the difference between the highest frequency heard by a student in the classroom and the initial frequency of the sound generator?
2. What is the difference between the lowest frequency heard by a student in the classroom and the initial frequency of the sound generator?
Describe the formation of galaxies.
Today's cosmologists assume that matter was not uniformly distributed in the universe after the Big Bang. Dense places attract more matter than the surrounding area according to their gravitational forces. Over the course of billions of years, these gas agglomerations eventually led to the formation of the galaxies we see today.
Consider a father pushing a child on a playground merry-go-round. The system has a moment of inertia of 84.4 kg.m^2. The father exerts a force on the merry-go-round perpendicular to its radius to achieve an angular acceleration of 4.44 rad/s^2.
Required:
a. How long (in s) does it take the father to give the merry-go-round an angular velocity of 1.53 rad/s? (Assume the merry-go-round is initially at rest.)
b. How many revolutions must he go through to generate this velocity?
c. If he exerts a slowing force of 270 N at a radius of 1.20 m, how long (in s) would it take him to stop them?
Answer:
Explanation:
Given that:
the initial angular velocity [tex]\omega_o = 0[/tex]
angular acceleration [tex]\alpha[/tex] = 4.44 rad/s²
Using the formula:
[tex]\omega = \omega_o+ \alpha t[/tex]
Making t the subject of the formula:
[tex]t= \dfrac{\omega- \omega_o}{ \alpha }[/tex]
where;
[tex]\omega = 1.53 \ rad/s^2[/tex]
∴
[tex]t= \dfrac{1.53-0}{4.44 }[/tex]
t = 0.345 s
b)
Using the formula:
[tex]\omega ^2 = \omega _o^2 + 2 \alpha \theta[/tex]
here;
[tex]\theta[/tex] = angular displacement
∴
[tex]\theta = \dfrac{\omega^2 - \omega_o^2}{2 \alpha }[/tex]
[tex]\theta = \dfrac{(1.53)^2 -0^2}{2 (4.44) }[/tex]
[tex]\theta =0.264 \ rad[/tex]
Recall that:
2π rad = 1 revolution
Then;
0.264 rad = (x) revolution
[tex]x = \dfrac{0.264 \times 1}{2 \pi}[/tex]
x = 0.042 revolutions
c)
Here; force = 270 N
radius = 1.20 m
The torque = F * r
[tex]\tau = 270 \times 1.20 \\ \\ \tau = 324 \ Nm[/tex]
However;
From the moment of inertia;
[tex]Torque( \tau) = I \alpha \\ \\ Since( I \alpha) = 324 \ Nm. \\ \\ Then; \\ \\ \alpha= \dfrac{324}{I}[/tex]
given that;
I = 84.4 kg.m²
[tex]\alpha= \dfrac{324}{84.4} \\ \\ \alpha=3.84 \ rad/s^2[/tex]
For re-tardation; [tex]\alpha=-3.84 \ rad/s^2[/tex]
Using the equation
[tex]t= \dfrac{\omega- \omega_o}{ \alpha }[/tex]
[tex]t= \dfrac{0-1.53}{ -3.84 }[/tex]
[tex]t= \dfrac{1.53}{ 3.84 }[/tex]
t = 0.398s
The required time it takes= 0.398s
SOMONE PLEASE HELP ASAP!!!!
violet
it has the shortest wavelength
The Nardo ring is a circular test track for cars. It has a circumference of 12.5 km. Cars travel around the track at a constant speed of 100 km/h. A car starts at the easternmost point of the ring and drives for 30 minutes at this speed.
Required:
a. What distance, in km, does the car travel?
b. What is the magnitude of the car's displacement, in km, from its initial position?
c. What is the speed of the car in m/s?
Answer: 50 km, 0, 27.78 m/s
Explanation:
Given
Circumference of the track is [tex]12.5\ km[/tex]
Speed of car is [tex]100\ km/h[/tex]
Car drives for [tex]30\ \text{minute}\ or\ 0.5\ hr[/tex]
(a)Distance traveled is
[tex]\Rightarrow D=100\times 0.5\\\Rightarrow D=50\ km[/tex]
(b)displacement of the car
It can be observed that 12.5 is a multiple of 50, that is, 50 km can be interpreted as 4 complete rounds of the track.
Therefore, the displacement of the car is zero.
(c)To convert kmph to m/s, multiply the entity by [tex]\frac{5}{18}[/tex]
[tex]\Rightarrow 100\times \dfrac{5}{18}\\\\\Rightarrow 27.78\ m/s[/tex]
Explain how newtons first law applies to the image to the left.
A box has base dimensions of 30 cm x 30 cm and a mass of 3 kg. Calculate to what
depth it sinks when placed in a tank of water (assume the sides are sufficiently high,
so that it floats). Density of water = 1000 kgm-3. Assume g=10 ms-2 for this problem.
Answer:
60
Explanation:
A box has base dimensions of 30 cm x 30 cm and a mass of 3 kg. Calculate to what
depth it sinks when placed in a tank of water (assume the sides are sufficiently high,
so that it floats). Density of water = 1000 kgm-3. Assume g=10 ms-2 for this problem.
An object is placed of 20cm from a concave mirror whose focal length is 10cm. what is the distance of image formed ?
Answer:
Answer 43cm
Explenation:
if you divide it to 4 it will convert to 43 so answer is 43cm if this wrong im sorry but mine is perfect thankss :)
Based on the number on the fuse, what do you think is the maximum current allowed in this circuit?
Answer:
0.3 A
Explanation:
Build the circuit attached. Make sure the switch is turned off as you build the circuit. Set the Selected battery voltage to 10 volts.
A. Based on the number on the fuse, what do you think is the maximum current allowed in this circuit?
Solution:
A fuse is a safety device which is used in circuits for preventing very high currents which can cause overloading or start a fire. A fuse is made up of a low resistance thin piece of metal such that the flow of high current can cause the metal to melt leading to an open circuit. A fuse lets current flow up to a maximum value before it melts and the circuit will be broken.
From the image attached, since the maximum rating of the fuse is 0.3 A, hence the maximum current that can flow through the circuit is 0.3 A.
a shopping bag can provide an upward force of 65N before breaking. A shopper puts 5 kg of groceries in the bag. If the shopper tries to lift the bag with an upward acceleration of 2 m/s/s, will the bag break?
Answer:
Since Force is Mass * Acceleration, the equation would be:
5kg * 2m^2 = 10N
(10N is less than 65N)
Therefore, it would not be enough force for the bag to break.
State the role of an electromotive force (EFF) in a current flow
Answer:
The emf source acts as a charge pump, moving negative charges from the positive terminal to the negative terminal to maintain the potential difference. This increases the potential energy of the charges and, therefore, the electric potential of the charges.
Explanation:
MARK AS BRAINLEST!!