Thursday, March 16, 2023

# How To Find Time In Physics

## Determining Tension On A Single Strand

Solving for time | One-dimensional motion | Physics | Khan Academy
• 1Define the forces on either end of the strand. The tension in a given strand of string or rope is a result of the forces pulling on the rope from either end. As a reminder, force = mass × acceleration. Assuming the rope is stretched tightly, any change in acceleration or mass in objects the rope is supporting will cause a change in tension in the rope. Don’t forget the constant acceleration due to gravity – even if a system is at rest, its components are subject to this force. We can think of a tension in a given rope as T = + , where “g” is the acceleration due to gravity of any objects the rope is supporting and “a” is any other acceleration on any objects the rope is supporting.XResearch source
• For the purposes of most physics problems, we assume ideal strings – in other words, that our rope, cable, etc. is thin, massless, and can’t be stretched or broken.
• As an example, let’s consider a system where a weight hangs from a wooden beam via a single rope . Neither the weight nor the rope are moving – the entire system is at rest. Because of this, we know that, for the weight to be held in equilibrium, the tension force must equal the force of gravity on the weight. In other words, Tension = Force of gravity = m × g.
• Assuming a 10 kg weight, then, the tension force is 10 kg × 9.8 m/s2 = 98 Newtons.
• Ft = Fg + m × a
• Ft = 98 + 10 kg × 1 m/s2
• Ft = 108 Newtons.
• Fc = m × v2/r
• Fc =10 × 2.67 = 26.7 Newtons.
• So, our the total tension would be 98 + 26.7 = 124.7 Newtons.
• T = 980/15
• ## Using The Wave Speed Formula

All electromagnetic radiation, of which visible light is one type, travels with a constant speed, denoted by the letter c, through a vacuum. You can write the wave speed formula using this value, and doing as physicists usually do, exchanging the period of the wave for its frequency. The formula becomes:

Since c is a constant, this equation allows you to calculate the wavelength of the light if you know its frequency and vice versa. Frequency is always expressed in Hertz, and because light has an extremely small wavelength, physicists measure it in angstroms , where one angstrom is 10 10 meters.

## Development Of The Second Minute And Concept Of A 24

The Egyptian civilization is often credited as being the first civilization that divided the day into smaller parts, due to documented evidence of their use of sundials. The earliest sundials divided the period between sunrise and sunset into 12 parts. Since sundials could not be used after sunset, measuring the passage of night was more difficult. Egyptian astronomers noticed patterns in a set of stars however, and used 12 of those stars to create 12 divisions of night. Having these two 12 part divisions of day and night is one theory behind where the concept of a 24-hour day originated. The divisions created by the Egyptians however, varied based on the time of the year, with summer hours being much longer than those of winter. It was not until later, around 147 to 127 BC that a Greek astronomer Hipparchus proposed dividing the day into 12 hours of daylight and 12 hours of darkness based on the days of the equinox. This constituted the 24 hours that would later be known as equinoctial hours and would result in days with hours of equal length. Despite this, fixed-length hours only became commonplace during the 14th century along with the advent of mechanical clocks.

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## Three Example Speed/distance/time Questions

• Andy drives his lorry for 400 miles, which takes him 8 hours. Harry drives 200 miles, which takes him 4.5 hours. Who is travelling faster?
• Answer: Andy is driving at 50mph, and Harry is driving at 44.44mph. So, Andy is driving faster.

• Tessa runs a 5km race with her running club every Saturday. She runs this in 40 minutes. If she maintains the same speed, how long would it take her to run the 8km race?
• Answer: Her speed is 7.5kph. If she runs 10km at 7.5kph, to work out the time, you need to divide 8 by 7.5, which equals 1.066. If we convert this into hours and minutes, it will take her 1 hour and 4 minutes to run 8km.

• Hannah goes on a cycling trip. In the first half of the journey, she travels at 10mph for 2 hours. In the second half, she travels at 20mph for 90 minutes. How far does she travel in total?
• Answer: In the first half of her journey she travels 20 miles . In the second half, she travels 30 miles, . 20+30 =50, so she travels 50 miles in total.

## The Alternative Origins Of Time Can the arrow of time be understood without invoking the past hypothesis? Some physicists argue that gravity not thermodynamics aims times arrow. In this view, gravity causes matter to clump together, defining an arrow of time that aligns itself with growth of complexity, said Tim Koslowski, a physicist at the National Autonomous University of Mexico . Koslowski and his colleagues developed simple models of universes made up of 1,000 pointlike particles, subject only to Newtons law of gravitation, and found that there will always be a moment of maximum density and minimum complexity. As one moves away from that point, in either direction, complexity increases. Naturally, we complex creatures capable of making observations can only evolve at some distance from the minimum. Still, wherever we happen to find ourselves in the history of the universe, we can point to an era of less complexity and call it the past, Koslowski said. The models are globally time-symmetric, but every observer will experience a local arrow of time. Its significant that the low-entropy starting point isnt an add-on to the model. Rather, it emerges naturally from it. Gravity essentially eliminates the need for a past hypothesis, Koslowski said.

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## How To Calculate Tension In Physics

In physics, tension is the force exerted by a rope, string, cable, or similar object on one or more objects. Anything pulled, hung, supported, or swung from a rope, string, cable, etc. is subject to the force of tension.XResearch source Like all forces, tension can accelerate objects or cause them to deform. Being able to calculate tension is an important skill not just for physics students but also for engineers and architects, who, to build safe buildings, must know whether the tension on a given rope or cable can withstand the strain caused by the weight of the object before yielding and breaking. See Step 1 to learn how to calculate tension in several physical systems.

## A Bike Starts To Move With An Initial Speed Of 30 M/sec And Acceleration Of 30 M/s2 After Time T Its Speed Is 90 M/sec How Much Time Is A Bike Required To Acquire Its Final Speed

Given,

initial speed 30 m/s

Final speed 90 m/s

Acceleration 30m/s^

Here we have given an in initial velocity, final velocity, and also the acceleration of a bike then use a first kinematical equation to find out the time,

We know that the first kinematical equation of motion is

V = u + at

90 = 30 + 30t

t = 2 sec

Hence bike requires 2 sec to acquire the speed of 90 m/s.

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## Concept Of Speed Distance And Time

To find the speed, we need distance traveled over some known time period. Thus speed is distance divided by time. To find the distance, we need to know the time and speed of the object. Thus distance is the product of speed with time.

Similarly, we can compute time during the motion to cover some distance with some known speed. This time can be calculated by dividing the distance with speed given. Speed is a very common concept in motion which is all about how slow or fast any object travel. Distance is directly proportionate to Velocity i.e speed of the object when time is constant.

These formulas are very simple but very important for computations.

## The Average Velocity Formula And Velocity Units

Different way to determine time in air | Two-dimensional motion | Physics | Khan Academy

The average velocity formula describes the relationship between the length of your route and the time it takes to travel. For example, if you drive a car for a distance of 70 miles in one hour, your average velocity equals 70 mph. In the previous section, we have introduced the basic velocity equation, but as you probably have already realized, there are more equations in the velocity calculator. Let’s list and organize them below:

• Simple velocity equation:
• Velocity after a certain time of acceleration:
• final velocity = initial velocity + acceleration * time

• Average velocity formula – weighted average of velocities:
• average velocity = velocityâ * timeâ + velocityâ * timeâ + …

You should use the average velocity formula if you can divide your route into few segments. For example, you drive a car with a speed of 25 mph for 1 h in the city and then reach 70 mph for 3 h on the highway. What is your average velocity? With the velocity calculator, you can find that it will be about 59 mph.

From the above equations, you can also imagine what are velocity units. British imperial units are feet per second ft/s and miles per hour mph. In the metric SI system the units are meters per second m/s and kilometers per hour km/h. Remember you can always easily switch between all of them in our tool!

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## S To Get Better At These Questions

In order to improve your skill in answering speed distance time questions, there are two main things you can do.

First, make sure that you are really familiar with the formula triangle. The key to answering these questions is knowing the formula inside out, so that you always know what equation to use, whether the exam question is asking you to work out speed or distance.

Secondly, you should focus on improving your general mathematical skills. You may get a compound question, which is one that asks you to use the formula in conjunction with other maths skills to work out the answer to the problem.

You can try a few maths practice tests, such as these, which will help you to practise your basic numeracy skills.

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## Period Of A Simple Harmonic Oscillator

The most basic type of periodic motion is that of a simple harmonic oscillator, which is defined as one which always experiences an acceleration proportional to its distance from the equilibrium position and directed toward the equilibrium position. In the absence of frictional forces, both a pendulum and a mass attached to a spring can be simple harmonic oscillators.

It’s possible to compare the oscillations of a mass on a spring or a pendulum to the motion of a body orbiting with uniform motion in a circular trajectory with radius r. If the angular velocity of the body moving in a circle is , its angular displacement from its starting point at any time t is = t, and the x and y components of its position are x = r cos and y = r sin.

Many oscillators move only in one dimension, and if they move horizontally, the are moving in the x direction. If the amplitude, which is the farthest it moves from its equilibrium position, is A, then the position at any time t is x = A cos. Here is known as the angular frequency, and it’s related to the frequency of oscillation by the equation = 2f. Because f = 1/T, you can write the period of oscillation like this:

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## Time Swept Under The Rug

There are a few things that everyone agrees on. The directionality that we observe in the macroscopic world is very real: Teacups shatter but do not spontaneously reassemble eggs can be scrambled but not unscrambled. Entropy a measure of the disorder in a system always increases, a fact encoded in the second law of thermodynamics. As the Austrian physicist Ludwig Boltzmann understood in the 19th century, the second law explains why events are more likely to evolve in one direction rather than another. It accounts for the arrow of time.

But things get trickier when we step back and ask why we happen to live in a universe where such a law holds. What Boltzmann truly explained is why the entropy of the universe will be larger tomorrow than it is today, said Sean Carroll, a physicist at the California Institute of Technology, as we sat in a hotel bar after the second day of presentations. But if that was all you knew, youd also say that the entropy of the universe was probably larger yesterday than today because all the underlying dynamics are completely symmetric with respect to time. That is, if entropy is ultimately based on the underlying laws of the universe, and those laws are the same going forward and backward, then entropy is just as likely to increase going backward in time. But no one believes that entropy actually works that way. Scrambled eggs always come after whole eggs, never the other way around.

## Period Is The Reciprocal Of Frequency The period is the time it takes for an oscillating system to complete a cycle, whereas the frequency is the number of cycles the system can complete in a given time period. For example, the Earth rotates once each day, so the period is 1 day, and the frequency is also 1 cycle per day. If you set the time standard to years, the period is 1/365 years while the frequency is 365 cycles per year. Period and frequency are reciprocal quantities:

In calculations involving atomic and electromagnetic phenomena, frequency in physics is usually measured in cycles per second, also known as Hertz , s 1 or 1/sec. When considering rotating bodies in the macroscopic world, revolutions per minute is also a common unit. Period can be measured in seconds, minutes or whatever time period is appropriate.

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## When Acceleration Initial Velocity And Final Velocity Are Given

Suppose a question provides a magnitude of acceleration, initial velocity, and final velocity of the object. In that case, the best way to calculate the time required to complete motion is by solving the first kinematical equation of motion.

Consider a car starts to move with an initial velocity and its final velocity , which accelerates within the motion. The magnitude of the acceleration is in the positive x-direction. Now to find out the time required to complete a motion, we use the first kinematical equation. The first kinematical equation of motion is,

A car moving in x-direction

Therefore,

u Initial velocity of a car

v Final velocity of a car

t Time required to complete the motion

a Acceleration of car

## Time In Quantum Mechanics

There is a time parameter in the equations of quantum mechanics. The Schrödinger equation is

Prerequisites
is Planck’s constant

The more precisely one measures the duration of a sequence of events, the less precisely one can measure the energy associated with that sequence, and vice versa. This equation is different from the standard uncertainty principle, because time is not an operator in quantum mechanics.

Corresponding commutator relations also hold for momentum p and position q, which are conjugate variables of each other, along with a corresponding uncertainty principle in momentum and position, similar to the energy and time relation above.

Quantum mechanics explains the properties of the periodic table of the elements. Starting with Otto Stern‘s and Walter Gerlach‘s experiment with molecular beams in a magnetic field, Isidor Rabi , was able to modulate the magnetic resonance of the beam. In 1945 Rabi then suggested that this technique be the basis of a clock using the resonant frequency of an atomic beam.In 2021 Jun Ye of JILA in Boulder Colorado observed time dilatation in the difference in the rate of optical lattice clock ticks at the top of a cloud of strontium atoms, than at the bottom of that cloud, a column one millimeter tall, under the influence of gravity.

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