The second (symbol: s, abbreviation: sec) is the base unit of time in the International System of Units (SI) (French: Système International d’unités), commonly understood and historically defined as 1⁄86400 of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds each. Analog clocks and watches often have sixty tick marks on their faces, representing seconds (and minutes), and a "second hand" to mark the passage of time in seconds. Digital clocks and watches often have a two-digit seconds counter. The second is also part of several other units of measurement like meters per second for speed, meters per second per second for acceleration, and cycles per second for frequency.
Although the historical definition of the unit was based on this division of the Earth's rotation cycle, the formal definition in the International System of Units (SI) is a much steadier timekeeper:The second is defined as being equal to the time duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the fundamental unperturbed ground-state of the caesium-133 atom.
Because the Earth's rotation varies and is also slowing ever so slightly, a leap second is added at irregular intervals to clock time to keep clocks in sync with Earth's rotation.
Multiples of seconds are usually counted in hours and minutes. Fractions of a second are usually counted in tenths or hundredths. In scientific work, small fractions of a second are counted in milliseconds (thousandths), microseconds (millionths), nanoseconds (billionths), and sometimes smaller units of a second. An everyday experience with small fractions of a second is a 1-gigahertz microprocessor which has a cycle time of 1 nanosecond. Camera shutter speeds are often expressed in fractions of a second, such as 1⁄30 second or 1⁄1000 second.
Sexagesimal divisions of the day from a calendar based on astronomical observation have existed since the third millennium BC, though they were not seconds as we know them today. Small divisions of time could not be measured back then, so such divisions were mathematically derived. The first timekeepers that could count seconds accurately were pendulum clocks invented in the 17th century. Starting in the 1950s, atomic clocks became better timekeepers than Earth's rotation, and they continue to set the standard today.
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...
Homework Statement
If it takes 17 seconds to blow up a balloon to 8 cm in diameter, how much longer will it take to inflate the balloon to 24 cm in diameter? Assume that the pressure that the balloon exerts on the air inside is proportional to the surface area of the balloon, that you blow...
Good evening. I am wondering if energy has always been quantized. I read that the shortest time after the Big Bang (the time it took for gravity to separate first) was 10^-43 seconds. At these moments of earliest symmetry breaking, was energy already discrete, or did quantum mechanics emerge...
Homework Statement
Hey, if a 1000 kg car is moving at 10 m/s brakes to stop in 5 seconds. What would the avergae breaking force be?
Homework Equations
The Attempt at a Solution
Hi,
I'm doing this algorithm questions and i need to find the largest size n of a problem that can be solved in time t, assuming that the algorithm to solve the problem takes f(n) microseconds.
For example:
f(n) = log n
t = 1 seconds
how do i get the largest size of n in t time...
Homework Statement
A boy dropped a stone at a pit. A sound was heard 2 seconds later. What is the distance of the bottom of the pit?
The Attempt at a Solution
Given:
Time - 2 Seconds
Vsound - 332m/s
332m/s * 2s = 664meters.
I think it is somewhat wrong. Maybe purely wrong. I...
I am a hobbyist, and I am not too familiar on to how to run motors. Can someone help me design a simple circuit that drives a dc motor on pulley drive of a conveyor belt. I only need a steady speed, I am not changing speeds. The conveyor belt has to stay on for 5 seconds after a switch is turned...
I am a hobbyist, and I am not too familiar on to how to run motors. Can someone help me design a simple circuit that drives a dc motor on pulley drive of a conveyor belt. The conveyor belt has to stay on for 5 seconds after a switch is turned on. The belt is about 48 inches long, the radius of...
SOLVED: Significant figures in seconds to hours calculation
Homework Statement
Not exactly a problem, but if I have minutes/seconds and am changing to hours, how many significant figures are there? For example: 29 minutes 57 seconds =0.499166667 hours needs ? significant figures.
The...
Homework Statement
A 3.0 kg metal ball is held 3.5m above the ground. Find the potential gravitational and kinetic energy of the ball after it is let go and has fallen for 0.4s
Homework Equations
EK= 1/2mv^2
EP=mgh
The Attempt at a Solution
Okay I know how to find both...
Hello,
Firstly, it's necessary to point out that I'm a Graphic Design student from the UK, and although I take a general interest in science and technology, my grasp of anything as academically demanding is nothing compared to what I expect of the forum members here, so I apologise if I seem...
Homework Statement
Skilled burglars have broken into a prosperous Swiss bank with the
intent of stealing a safe filled with gold. The entire safe, i.e. safe
and gold, weighs one metric ton. The burglars managed to find the
safe and they brought it to a large floor-to-ceiling window. Their...
Homework Statement
The space shuttle undergoes an acceleration of 53.9 m/s^2. How fast is it traveling at the end of 55.2 s?
Homework Equations
The Attempt at a Solution
I have no clue. I am doing a summer assignment and it is very poorly explained by the teacher.
Homework Statement
A passenger train is approaching a railway crossing from 105m to the east, at 54km/h. Meanwhile a train approaches from 140m to the north, at 72km/h. How fast is the distance between them changing after 5 seconds?
Homework Equations
Pythagorean Theorem?
The...
Homework Statement
Determine the acceleration after 6 seconds.
Homework Equations
s(t) = sqrt12t - 8 where s is in metres and t is in seconds.
The Attempt at a Solution
v=s'(t)=6/sqrt12t-8
this is where i don't understand...they got a positive value for 36 in the book...
Homework Statement
A ball falls from the top of a building.
It falls past a window. It is in view for .16 seconds.
The window is 1.7 m long.
How high was the building off which it was dropped?
Homework Equations
I'm trying to use
.5 a t^2 + vt + x
but it's not working
The...
Homework Statement
I'm attempting to find the orbital radius for a binary system based on the parallax of the system and angular seperation:
1. A visual binary system that is 5 pc away is seen edge-on (i.e. we are in the plane of the orbit). The maximum angular separation of the two stars is...
Homework Statement
Traveling at a speed of 180.7 km/hr, you only have about 1/2 km until you reach the curve. At this speed, how many seconds do you have until you reach the curve? Don't forget to convert your answer to the correct units.Homework Equations
t = d/v ??The Attempt at a Solution...
Greetings,
Before I begin, I'd like to mention that I am in a High School level physics course (AP Physics B 32S), so my level of knowledge is quite low. This is not for coursework, but for discussion.
In an informal discussion with my instructor outside of class, we were talking about...
1. (a)The speed of the tip of the minute hand on a
town clock is 0.00136 m/s.
What is the speed of the tip of the second
hand of the same length?
Answer in units of m/s.
(b)What is the centripetal acceleration of the tip
of the second hand?
Answer in units of m/s2.
Homework...
Homework Statement
I have put the diagram in an attachment. I need to find position at 8 seconds.Homework Equations
X = ½ at² + vt + x
The Attempt at a Solution
-34m + (-3m/s)(8.0s)+ ½ (-4.0m/s2)(1.0s)2 = -165 meters
We got some cool weather today along with some scattered showers. My wife was sitting there in deep concentration so I asked her what she was thinking. She said she was counting the seconds between the lighting flash and the thunder. She said that the light gets here much faster than the sound...
Homework Statement
A rocket has launched straight up, and its altitude is h = 10t2
feet after t seconds. You are on the ground 1000 feet from the launch site. The line
of sight from you to the rocket makes an angle θ with the horizontal. By how many
Radians per second is θ changing ten seconds...
Homework Statement
Consider a bead of mass m that is free to move around a horizontal, circular ring of wire (the wire passes through a hole in the bead). You may neglect gravity in this problem (assume the experiment is being done in space, far away from anything else). The radius of the ring...
Hey everyone
I got a problem. There is a line that provides 12VDC power in 1 second intervals (On and then Off, yes a signal light). The thing is I want to connect a relay to it but the relay must not turn off and on with the signal light.
I was thinking of using a capacitor but I don't know...
I've seen in many places that inflation is believed to begin around 10^{-36} s corresponding to the end of the grand unification epoch. Why do we believe that this is the time that it started? Isn't the only requirement that it start sometime after Planck time 10^{-44} s?
Thanks!
Homework Statement
A ball is projected horizontally from the top oF A CLIFF WOTH SPEED U. iF AIR RESISTANCE IS NEGLECTED AND G IS ASSUMED to be 10 ms-2, the velocity of the ball is found to be 50ms-2, 3 seconds later. What is the value of uHomework Equations
s=ut+1/2at2
s=vt
v2=u2+2as
v=u+at...
Hi guys,
My problem is that i have a motor that needs to be turned ON once, every day at a programmable time and for a duration of 10-20 seconds. The power of the motor is bellow 80W.
I have searched throught the net on Merlin Gerin, Schrack and similar catlogues but can't find any...
I asked this of my maths lecturer in uni. He took about ten seconds to mentally perform the calculation/integration. Can you beat his time?
Q.
A cyclist rides 100 miles from point A to point B at a constant velocity of 20mph. As he leaves point A, a bee on his handlebars flies ahead of him...
Hello everyone.
I got a speeding ticket for doing 53mph in a 35mph zone. (he origionally said 55mph so both calculations would be great) I was at a dead stop he said I punched it and got to 55mph before he pulled me over. My truck is a 2007 tundra that goes 0-60 in 6.7 seconds and the quarter...
Homework Statement
There is an attachment for the picture. question is, How many revolutions does the object make during the first 4 s?
Homework Equations
The Attempt at a Solution
I attempted to solve this by dividing 20 by 2pi, but apparently, that was wrong. Any help?
Im doing a paper due tomorrow. I wanted to include something I remember DaveC talked about long ago. I searched, and searched, and searched. And I had to wait 30 seconds each time! :grumpy:^:mad:
Finally, I got it!
http://en.wikipedia.org/wiki/Square-cube_law
What a colossal waste of...
Homework Statement
A projectile is fired with an initial speed of 68 m/s at 37 degrees above horizontal on a flat firing range. c) Determine speed of the projectile 2.3 seconds after firing. d) Determine direction of projectile 2.3 s after firing.
Homework Equations
c) Vox=Vx=68m/s...
A helicopter holding a 70-kilogram package suspended from a rop 5.0 meters long accelerates upward at a rate of 5.2 m/s^2. neglect air resistence on the package. When the upward velocity of the helicopter is 30 meters per second, the rope is cut and the helicopter continues to accelerate upward...
if it takes me 60 seconds to make a cup of tea, and my manager wants me to make it 25% faster, does that mean i make it in
a) 60/1.25 = 48 seconds
b) 60*0.75 = 45 seconds
some people say a, some people say b. What do you guys think?
I think personally think it's a.
If someone told you...
I was at tattershall lakes the other day and a skier went over a jump, about 3 seconds later after he landed you'd hear the slap of his skis hitting the water.
I want to know why? I know that light travels faster than sound, but we wasn't very far away, not far enough for it to make that...
Hello.
This is not a Physics homework problem, but rather a Programming project. I am asked to model a pendulum using the Java Swing class for graphics, but I'm having a few problems understanding the Physics behind it, and would appreciate a few answers and some guidance.
Doing the...
Homework Statement
If a stone is thrown vertically upward from the surface of the moon with a velocity of 10m/s, its height (in meters) after t seconds is h = 10t - 0.83t^2.
a) What is the velocity of the stone after 3s?
b) What is the velocity of the stone after it has risen 25m...
Hello,
I've tried looking this up on Google but haven't found anything of relevance.
Basically, I want to know what the unit "Voltage Seconds" (Voltage x Seconds) resembles, if it does.
Thanks
1. A bullet is fired horizontally from the roof of a building 100. meteres tall with a speed of 850 meters per second. Neglecting air resistance, how far will the bullet drop in 3.00 seconds?
1) 29.4 m 2) 44.1 m 3) 100. m 4) 2,550
Since the horizontal speed should be constant throughout, so...
ProblemFor the information given below estimate the velocity of the car over the 10 second interval using 5 subintervals and midpoints.
Car velocity and time:
time (t) velocity
0 0
1 20
2 35
3 48
4 62
5...
Suppose that I have an aluminum cube with side lengths 10 cm. Suppose that I uniformly and continuously apply a temperature of 60 degrees celcius to one of its sides. The medium surroudning it is air with a temperature of 27 degrees celcius. After t seconds, what is the temperature of the...
Hi, everyone.
I am currently involved in a small electronics project and I am required to produce a time delay for part of the project. I plan on using the famous 555 timer and not quite sure on what to do to produce this delay.So please anyone help explain how to produce a time delay of,say...
How many revolutions does the object make during the first 4 s
well the area under the graph of the angular velocity versus time graph is 60
but I do not know how that helps.
Any help would be appreciated.
Stephen
I just read that the Gregorian calendar is off by 26 seconds a year from the solar calendar. That adds up to about 43 minutes ever 100 hundred years.
Does this mean that if it starts to get dark at 5:30 pm on the East coast on December 1st, that it got darker 43 minutes earlier or later 100...
If
The second is currently defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom.
And
The meter is defined as 1⁄299 792 458 of a light-second.
Then
Why can't we...