Seconds Definition and 119 Threads

Reading this PDF from Professor Richard Conn Henry, I am confused by the multiplication by c on page 2. x, y and z are metres. t has units seconds. So I would think, "We can't subtract seconds from metres , we can't subtract dt from dx." To sidestep that, Einstein multiplied dt by c. c has...

Hi everyone, i have been trying to find an answer to this problem I have but couldnt find any good answers... (I dont know much about this stuff, but need a formula for a Project I am currently working on). So The problem goes as follows: Assuming we have a ball with a mass of m which is...

Using the above formula I get that the time goes 6.5∗10−86.5∗10−8 percent faster in ISS. Thus, this is approximately 2 seconds in a year. But the answer is much lower. Where am I making a mistake?

This the answer key:: im confused because it say "how much energy has been dissipated after 5s". So shouldn't you be looking at the ground after 5 sec. but apparently the solution look at it before 5 sec, am I missing anything, can someone explain

r = 0.25m I = 7.14kgm^2 h = 6.01m Ei = Ef mgh = 1/2mv^2 + 1/2Iw^2 2mgh = mv^2 + I(v^2/r^2) 2(35.8)(9.81)(6.01) = 35.8v^2 + 114.24v^2 v = 5.304 m/s v = d/t 5.304 = 6.01/t t = 1.133 (The correct answer is 2.2673. What did I do wrong?)

In the twin experiment, the travel time is shorter for the traveling brother than for the static brother. Since the unit of time in physics is the second, is the travel duration shorter because: (1) it contains fewer seconds or (2) the number of seconds is the same for both brothers but the...

I have a problem: in the same anime I saw that Senku estimated the time to start burning the paper in sixty seconds, one minute and with a lens. The data is as follows: The lens he used has a diameter of 5 centimeters. The solar constant, assuming it is the same as 3700 years ago, is 1362 watts...

Figure given in question-: I first found out the time when force will be equal ro friction.After force becomes equal to friction there will be no acceleartion further,so velocity after that time will be same.I calculated the velocity by getting a relation of it with time.I got the velocity as...

Homework Statement Train starts to travel in a straight line at increasing speeds. The first wagon passes next to me in 4 seconds. In how many seconds will the n-th wagon pass next to me? Homework Equations s= vo.t + 1/2at^2 v= vo + at The Attempt at a Solution First of all we didn't learn...

Something was thrown with an elevation angle $$60^{\circ}$$. Determine its velocity and direction after: a. $$\frac{1}{2}\sqrt3$$ second b. $$\sqrt3$$ second I tried solving the (a) question by substituting the angle to the equation $$y=v_0\sin\alpha t-\frac{1}{2}gt^2$$ and got 0 (the book uses...

Hi, I need to convert a value of 12*10-16 m7 N-3 y-1 to the units of kPa-3 m2 s-1. Can anyone help me? where: m = meters, N = Newton, y = year, s = seconds. Thanks!

$\tiny{Embry-Brittle \, 12}$ $\textsf{A car, starting from rest, accelerates in a straight line at a constant rate of $\displaystyle 2.0 \frac{m}{s^2}$}$$\textit{How far will the car travel in $10$ seconds}$\begin{align*}\displaystyle \Delta t&=10\\ a&=2\\ d_i&=0\\ v_i&=0\\...

Homework Statement Homework Equations V = L di/dt Energy = V*I*t The Attempt at a Solution First we find out V across L This V will be there only for 1st 2 seconds as after that there is no change in current. So V(across L) is L * di/dt = 2 * 6/2 = 6V equation 1 Now Current is a function...

Reduce the following numbers of radians to degrees, minutes, and seconds. (a). 0.47623. (b). 0.25412. Can someone work out (a) in steps? I can then use it as a guide to solve (b).

Express the following angle in radians. 12 degrees, 28 minutes, 4 seconds that is, 12° 28' 4". I cannot apply pi/180° to this problem.

Homework Statement (a)Estimate the number of photons per second emitted by a 100-W lightbulb, assuming a photon wavelength of 550nm.(b) A person can just see this bulb for a distance of 800m, with the pupil dilated to 7.5mm. How many photons per second are entering the pupil? Homework...

Homework Statement With what speed should a body be thrown upward so the distance traversed in the 5th second and 6th second are equal? Homework Equations No idea since I fail to comprehend the statement of the problem. The Attempt at a Solution This doesn't make sense to me, the distance...

Homework Statement A football punter can punt a maximum range of 40.8 m. If he instead wants to punt only 34.6 m, but maximize the time the ball is in the air, at what angle from the horizontal should he kick the ball, and how long will it stay in the air if he hits it perfectly? (neglect air...

Homework Statement A shaft is turning at 65.0 rad/s at time zero. Thereafter, its angular acceleration is given by α = -10 rad/s 2 - 5t rad/s 3 where t is the elapsed time. (a) Find its angular speed at t = 3.00 s. (b) How far does it turn in the 3.00 s seconds? t=3 seconds wi= 65.0 rad/s α =...

I have a video to present to my class and for five seconds it goes all blurry. Does anyone know how to sort it out and why it happened?

Homework Statement An object is thrown horizontally and after 3 seconds the speed vector forms the angle pi/4 radians with the horizontal direction. FInd the speed after 4 seconds. Homework Equations v=gt The Attempt at a Solution As it forms the angle pi/4 radians, vx=vy, so v0=gt=3*10=30 vy...

Homework Statement The particle is thrown horizontally with speed 10 m/S (I believe from a height). Find the speed of it after 0.2 seconds. Homework Equations vx=v vy=gt v=sqrt(vx^2+vy^2)[/B] The Attempt at a Solution vx=10 vy=10*0.2=2 v=sqrt(100+4)=10.198m/S Am i right?

I am on Alpha 4 light years away from earth. On 1st Jan, 2016 I lit a powerful laser light towards Earth for 10 seconds and then switched it off. My friend on Earth knows that he has to detect that light after 4 years on the night of 1st Jan, 2020 from a space station using a very powerful...

Homework Statement Write three functions int get_hour(int timestamp), int get_min(int timestamp), int get_second(int timestamp) which will respectively return the hour of the day, the minute of the hour, and the second of the minute from a value given as parameter which is in milliseconds...

Homework Statement The police was headed to a felony and passed you so you stopped. What frequency did you hear 3 second after the police passed you? Homework Equations f=1/T The Attempt at a Solution f=1/3 f=.33Hz

Using an ablative carbon-carbon heat-shield, what thickness would be used up? Or might a ceramic insulator be able to handle it? What would happen if the nose was solid aluminium?How can this be calculated? What information do I need to figure this out?

Homework Statement To escape the fire which has just declared itself in the building, James jumps through the window. One second before reaching the mattress, he traveled half of the height of fall. What is the total time of the fall in seconds ? What is the total height of the fall in meters...

Homework Statement Ignoring air drag, how fast must you toss a ball straight up for it to take 2 seconds to return to same level you threw it from. 1. 20 m/s 2. 7.5 m/s 3. 15 m/s 4. 5 m/s 5. 10 m/s Homework Equations vf = vi + a x t The Attempt at a Solution To me this problem seems...

Homework Statement (42°12'13'')+(59°56'15'')+(257°51'35'') Homework EquationsThe Attempt at a Solution 42°12'13'' 59°56'15'' 257°51'35'' -------------- 358°228'63'' +3° +1' -60'' --------------- 361°229'3'' -180' --------------- 361°49'3'' The answer is 360°0'3'' Where did I go wrong?

Homework Statement Convert 1 ##Gev## to Kelvin, and convert ##GeV^{-1}## to meters, seconds, and convert ##GeV^4## to density ##(kg/ m^3).## Homework Equations natural units ##c=h=k_B=1## The Attempt at a Solution I know to convert energy to meters, I can use ##\lambda =hc/E##, I get the...

Homework Statement Two cars are initially 17.50 km apart on a straight road. If the cars are moving toward each other, car 1 with a speed of 7.50 m/s and car 2 with a speed of 10.40 m/s, how many seconds will it take before the cars meet? Round your answer to three significant figures...

If I have a voltage magnitude that I can modify, say I'm measureing the RMS of it. And that it is at a set frequency, and I want to know the quantity (that I am only just familiarising myself with) known as volt-seconds, on a coil and magnetic core. Say I was looking at how many volt seconds the...

As part of an EMT shift at an athletic event yesterday, I took vitals on a 45y/o female Pt who had completed the stressful event about 30 minutes prior. She is very fit and experienced in athletic competition. When I was auscultating her BP, I thought that it sounded like she was skipping some...

Sand falls on to horizontal ground at the rate of $$9m^3$$ per minute and forms a heap in the shape of a right circular cone with vertical angle $$60^{\circ}$$. Show that 10 seconds after the sand begins to fall, the rate at which the radius of the base of the pile is increasing is...

< Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown >[/color] Okay, I am having trouble with the units. I have the values for the wavenumber and I am trying to find the period. These are the formulas that I am trying. T = 1/f ; f = c/lambda...

I am solving some problems of my physics book for fun and for some reason I am getting a wrong answer from this one. 1. Homework Statement A bullet is shot at an angle of 35o with a speed of 90 m/s. I assume that air resistance is ignored. Calculate bullet's distance from launch site 2,5...

Homework Statement A car starts from rest and accelerates uniformly at 3.0 m/s2. A second car starts from rest 6.0 s later at the same point and accelerates uniformly at 5.0 m/s2. How long does it take the second car to overtake the first car? Homework EquationsThe Attempt at a Solution So let...

When thinking of a spherical shaped particle moving about under Brownian motion, one describes its motion by Diffusion. The units being \frac{m^2}{s} I can understand this physically as a distance it will travel from a certain point in space averaged over x-y and z direction. Now rotational...

Homework Statement Nothing travels faster than light, which manages to get to the moon from the Earth in 1 second. However, we can still get there in a shorter amount of time. How fast would we have to travel to reach the moon in 0.9 seconds? Homework Equations I know the question is weird but...

Hi! I wonder why it is so hard to make a fusion reaction last for more than a few seconds. I have read a few elementary courses in Plasma Physics but do not remember so much. What I do rememeber is that they said that whenever a fusion reaction starts within a Tokamak the plasma tends...

Hi, I am trying to create a laboratory scale system, where I would like to deliver 0.25 mg of a substance which is granular and powder like consistency. I would like to pulse it for a few seconds and stop it. Can anybody tell me a good delivery mechanism for this. I have a method to disperse...

Homework Statement Given an equation such as f(t)=Rsin(ωt + θ) find the value of f(t) when t=5s Homework Equations N/A The Attempt at a Solution What I'm not understanding is that generally a function sin(ωt + θ) describes what happens when the angle t changes. However the...

A human cannonball was fired from a cannon with a muzzle velocity of 107 km/h. The firing angle was 45 degrees from the horizontal Ive converted 107 km/h to 29.71 m/s 1.How many seconds did it take for the human cannonball to reach maximum height? 2.How high did he rise? h =...

Homework Statement Ok, so I am doing areas between curves, but one of the functions is y=50/(25+x^2) This is stupid, but I THINK I am having trouble finding the anti-derivative (I just know my final answer is wrong, but I'm pretty sure it is related to this.) The Attempt at a...

So the differential equation I have to solve using power series is y''-xy=0 when x0 = -1 So i set it up Ʃ(n+2)(n+1)an+2(x+1)n - x Ʃ an(x+1)n I know how to generally solve equations like this, but I never solved one like this, where I have to distribute the x ... x(x+1)n ... I just...

Homework Statement You are in a car that is on the top of a steep 500 meter high hill. You are stepping of the brakes so your car is not moving. How much energy per second( power) must be expended to keep the car stationary Homework Equations The Attempt at a Solution

Does the back emf in a dc motor start to appear after a slight delay(say 1 or 2 seconds) after starting up the motor? I have had this simple doubt for a long time.According to the "generator principle" both applied emf and back emf will always exist simultaneously.Also it would be in violation...

Homework Statement In the equation z = ct + d, z is measured in meters and t is measured in seconds. What are the dimensions (units) of d? answer options are... s/m, m/s, m, s, m*sHomework Equations The Attempt at a Solution plugged in m for z, s for t, and m/s for c. solved for D and got 0.

The question is: A 56.0 kg bungy-jumper hangs suspended from her bungy-cord, at rest. She is displaced from this position by 15.0 m downward, and then released. She bounces up and down, with a period of 5.800 s. Assume the woman undergoes simple harmonic motion, described by y(t) = X cos(2...

Homework Statement Body's linear equation of motion is s= A + B*t + C*t^3 (A= 2.0m, B = 3.0 m/s, C = 0.010 m/s^3) What is the velocity and acceleration of a body on t= 0 s and t = 10 s. Calculate the velocity and accelerations average values within first 10 seconds, starting from start of the...