Physics regards the physical aspects of the natural world. It includes topics that deal with forces on different bodies within the universe and phenomena that explain how the universe works.

242,756 Questions

What happens to the temperature of naphthalene during melting?

Lab: Melting / Freezing Point of NaphthaleneObjective: In this lab, you will investigate the melting and freezing point of the substance, naphthalene (moth ball flakes). You will heat solid naphthalene and record temperature changes and examine the graph to determine the melting point of the substance. You will then cool naphthalene and record temperature changes in order to determine the Freezing point of the substance

Part A: What happens to temperature as naphthalene melts?

Objective: As heat is applied to liquid naphthalene, the temperature rises. As the temperature rises, the naphthalene will eventually start to melt. This lab experiment tries to answer the question: what happens to the temperature of naphthalene as it melts? In this lab, you will heat the liquid naphthalene, and record the temperature changes. You will graph the temperature changes before drawing any conclusions.

Part B: Determining the freezing point of naphthaleneObjective: Freezing point is a characteristic property of matter. As heat is taken away from a liquid, the temperature of that liquid decreases as the substance begins to freeze. This lab experiment tries to answer the question: what is the freezing point of an unknown liquid (naphthalene)? In this lab, you will cool liquid naphthalene, and record the temperature changes. You will graph the temperature changes before drawing any conclusions.

What energy transformation occurs when you ring a bell?

the potential energy from the object hitting the bell becomes kinetic energy which becomes mechanical energy which becomes sound


How were you able to increase the amount of potential energy the ball had?

As we increase the altitude of the ball the potential energy increases.

Meteorology and Weather

Why is the sky blue?

Because during day time our atmosphere scatters red light and bluish appearance is
Example Sentences

How do you use attenuation in a sentence?

After his heart transplant, he was given special medicine to prevent rejection, these drugs are to be taken daily in order for attenuation to take place and to attenuate the immune response and to keep the body from rejecting its new heart.

Installing this new piece of equipment will let through the lower frequencies, therefore achieving attenuation.


The forces of attraction between two objects varies with what two factors?

Depends on the force but for gravity the answer is mass and distance.


What device or instrument is used to measure air pressure?

Plastic Bag or any object that can be inflated.


What is the Example of digital quantity?

A digital quantity example is provided by any digital microprocessor display where a discrete number is provided and the actual value is an irrational number.

Some examples are the computer display of the values of pi, the square root of 2, the quotient of 3/19, or any other irrational number.

A computer basically works with the integers 0 and 1, so it is a "digital" machine (it cannot deal with 3/19, or pi, etc with perfect accuracy).

Social Sciences

What is the movement of organisms from one place to another?

Lentiviruses are very efficient at delivering genetic materials to both dividing and non-dividing cells. According to whether proviral DNA is formed in transduced cells, lentiviruses can be further divided into two groups: integrating lentivirus (ILV) and integrase-deficient lentivirus (IDLV). ILV is first developed and applied in scientific research and IDLV is constructed later through genetic modification.

Which science is the most complex chemistry or biology or physics?

biology because it tells us what is important to humans and biology is more easier than physics and chemistry

Space Travel and Exploration
Science Experiments
Sound Waves

What is the speed of ultrasound waves in the air?

The 'normal' speed of sound is 340 m/s in dry air at room temperature and pressure.

From your question, it appears we should differentiate the terms "ultrasonic" and "supersonic".

Ultrasonic relates to sonic frequencies higher than 20 KHz, i.e. beyond audible range. For a given gas, the speed of sound is independent of the frequency of the sound measured and also independent of the density of the gas.

Supersonic relates to a speed of an object greater than the normal speed of sound (340 m/s in air at STP) and usually the phenomena associated with it.

The speed of sound is also a functionof the medium through which it's passing. For example, the speed of sound through water is 1,500 m/s, and is slightly over 5,000 m/s in iron.

So to answer your question, the speed of ultrasound in airis340 m/s for the reasons given.


Which term describes the tendency of an object to resist a change in motion?

An object's tendency to resist a change in its state of motion is called inertia. This is the basis of Newton's Laws of Motion; "An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.". The state of motion refers to the object's velocity, which is the the speed and direction. One quantifies inertia as the quantity of mass of an object. On can say that the mass of an object is a measure of how much an object resists change in its motion. The more mass an object has, the more inertia it has. That's why it is harder to push a 3 ton box as opposed to a soccer ball, or something lighter.

Botany or Plant Biology

Science investigatory project of avocado leaves?

You can try to find a use for avocado leaves like observing if it is good at repelling mosquitoes or if it will make a fire last longer or something like that.

Math and Arithmetic

What is bigger 3.6 m or 36 cm?

3.6 m is bigger

Thunderstorms and Lightning

Is it safe to take a shower during a thunderstorm?

No—in fact, the CDC encourages avoiding all water in your house during a thunderstorm. Your plumbing and the water coming out of it can conduct electricity if lightning strikes your home, and that can lead to you getting seriously hurt. Granted, this is a pretty rare occurrence, but experts still advise against it as an easy way to avoid something potentially fatal. You should wait half an hour after hearing the last boom of thunder before hopping into the shower.

Chemical Bonding

Why does water have a high and specific heat capacity?

First, we need to know a little bit about water. Water is a polar molecule because oxygen bears partial negative charge and hydrogen bears partial positive charge. This results in extensive hydrogen bonding in water molecules between slightly negative oxygens and slightly positive hydrogens. Second, we need to remember that temperature is another way of saying the average kinetic energy of particles - the higher the temperature, the faster they move, in the case of gases and liquids, or vibrate, in the case of solids. Third, heat capacity is the ability of matter to absorb thermal energy. One calorie is defined as the amount required to heat a gram of water one degree Centigrade. That same calorie will heat a gram of gold 33 degrees.

Water's specific heat is defined as 1. The specific heat of gold is therefore .03. Water has a high specific heat because there are quite a few ways water can store heat. 1. Moving along three axes 2. Rotating the "V" shaped molecule in three different directions 3. Hydrogen atoms vibrating back and forth like a tuning fork 4. Hydrogen atoms vibrating up and down along their H-O axis.

Finally, the heat of fusion of water is 80 calories per gram, and the heat of vaporization for water is 540 calories. So ice can absorb 80 times as much heat while melting as the same mass of water. Water absorbs 540 times as much heat while turning into water vapor as the same mass of water absorbs. Both phase changes occur at constant temperature, 0 Centigrade and 100 Centigrade respectively. Look up phase change graph for water to see the interesting line.


What kind of a simple machine is a toothbrush?

A toothbrush is not a simple machine, it does not work on the principle of levers, effort, and load.

It's not a machine at all in mathematical terms. A "machine" is that which performs "work", i.e. transfers or converts energy.

You arm moving the toothbrush is a machine by this definition, however.

Nuclear Physics
Particle Physics

Matter attracts other matter does antimatter will repel the antimatter?

Antimatter observes and obeys the same fundamental forces that matter does:

  • gravity
  • electromagnetism
  • weak interactive
  • strong interactive

A positron, which is the anti-particle of the electron, for example, has the same mass as an electron and experiences the same attraction to all other matter (gravity) as an electron. That same positron is repelled by positively charged particles and attracted to negatively charged particles (electromagnetism).
Stephen Hawking

What is Stephen Hawking's IQ?

Although Professor Hawking discounts the value of numerical IQ's, he admitted that his own is likely very high (it has been suggested as 160 or more). He also said that "People who boast about their IQ's are losers". (see link to 2004 interview)

---a possibly dramatized anecdote from Introducing Stephen Hawking (2006)---

Near the end of his term at Oxford and no doubt beginning to feel the effects of ALS, Hawking took a terrible fall down a staircase in the university hall. As a result, he temporarily lost his memory. He could not even remember his name. After several hours of interrogation by his friends, he finally returned to normal but was worried about possible permanent brain damage. To be sure, he decided to take the Mensa test for individuals with superior intelligence. He was delighted to find that he passed with flying colours, scoring between 200 and 250!

Math and Arithmetic
Weight and Mass

What is mass divided by weight?


Newtons Laws of Motion

What is the formula for calculating acceleration?


There are a few. The most famous is a = F/m, where F is the net force applied to a mass, m.

Acceleration is also the change in velocity, (Delta-V), divided by the change in time, (Delta-t). So, a =Δv/Δt.

For example, if an object's velocity changes from 10 meters per second to 20 meters per second in five seconds, its acceleration is (20-10)/5 = 2 meters per second per second, or 2 meters per second squared (m/s2).

For circular motion, centripetal acceleration is v2/r, where v is the linear velocity of the rotating object and r is the radius of its circular path.

Equations in a nutshell

Constant Accelerationa = Δv/Δt = (vfinal - vinitial) / (tfinal - tinitial)

a = (v2-u2)/2s

a = 2(s - ut)/t2


a=acceleration (m/s2)

v=final velocity (m/s)

u=initial velocity (m/s)

t=time (s)

s=distance (m).



a=acceleration (m/s2)

v=final velocity (m/s)

vo=initial velocity (m/s)

t=time (s).

Newton's Second Law

F = ma, thus, a = F/m

Centripetal Acceleration

ac = v2/r

Warning: Calculus Speak:

Acceleration is the second derivative of position with respect to time: d2x / dt2, which makes it the first derivative of velocity: dv / dt. Therefore, the acceleration is the slope of the curve on the velocity-versus-time graph.


a = dv / dt = d2x / dt2

Acceleration is a quaternion with real and vector parts:

a= (V^2/R - cDel.v)) + (dcv/dR + cDelxv + V^2/R r)

a= (V^2/R - cV/R cos(v)) + (dv/dt + cv/R sin(v) + V^2/R r)

where R=ct and dR=cdt.

cv/Rcos(v) is the Centrifugal Acceleration a part of the real accelerations in the first parenthesis. The second parenthesis contains the vector accelerations.

Acceleration = F/m, where F is the net force applied to a mass, m.


acceleration in terms of velocity.

a = v - u/t Delta Velocity divided by Time.

A = ΔV ÷ T Acceleration is worked out by (final speed - initial speed)/ time taken for change in speed a = v2-v1/ t2-t1 Strictly you should say velocity ie the speed in a certain direction. Youalso have the formula f=ma which tells you that the force needed to get something moving will be the mass of the object multiplied by the accelertion you want to achieve; so from this formula if you know force and mass you can work out acceleration. The formula for acceleration is: Vf-(Vi)/t ie. change in velocity per unit time. Instantaneous acceleration in its differential form is d2x/dt2 where x is a function of time t.

Acceleration is the time rate of change of velocity.

That is, acceleration =dv/dt (v - velocity ; t - time)

Or simply acceleration = change in velocity / time


What instrument measures temperature?

Most commonly, a thermometer.

Related Information:

Thermometers are used to measure the increase or decrease in the temperature of a system as it gains or loses internal energy.

An alcohol-in-glass thermometer has been the most common personal instrument used to measure temperature. Mercury thermometers are still around but are no longer offered for sale. Today, digital devices are available that scan the forehead or ear. Some other devices used to measure temperature are:

Radiation pyrometer, for extremely high temperatures;

Glass thermometer: mercury or alcohol;


Thermistor (thermal resistor)

Bimetallic strip;

Bimetallic spiral;

Platinum resistance thermometer (a resistance detector);


A mercury in glass thermometer uses mercury liquid contained within its glass structure to be subjected to heat.

the heat causes the mercury fluid to expand along the glass tube

and the total amount of expansion can be seen as a measure

along the accurate scale of indication.

This is a direct indication of the effects of temperature.

A more complex method of measuring temperature could be a

thermocouple measuring device.

A thermocouple consists of 2 dissimilar types of metal materials in the form of wires , which are joined at 1 end by weld/ fusion.

this single joined end is called the hot junction. The other end of the 2 wires are then terminated at separate junctions;

as in a electronic terminal block. This end of the 2 wires can be called the cold junction.

For most accurate temperature measure, I think temperature sensor is the first choice.

Atoms and Atomic Structure

What is the temperature of a lighter flame?

The temperature of a Bic lighter flame is 1977 C or 3590.6 F.

Solid State Physics

What is dislocation density?

Dislocation density is the areal density of dislocations intersecting a plain, usually the free surface, given as number per cm2.

It may also be the volume density of dislocation line segments, given as the total length of dislocations divided by the containing volume (also 1/cm2), but this is rarely used in semiconductor physics, and more frequently found in engineering.

Dislocation density is typically measured by etching the free surface to form pits around the location at which the dislocation breeches the surface, and is termed etch pit density, or EPD.

Quantum Mechanics

Why are leptons divided into families?

Leptons are divided into three families with 4 particles (2 particles, plus their two anti-particles) in each family. In the electron family we have the electron, positron, electron neutrino and electron anti-neutrino. Each family has a higher mass than the one before it so the tauon is heavier than the muon which is heavier than the electron. The physical reason for there being three families is completely unknown and will probably win you a Nobel prize if you can figure it out!


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