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Physics Interview Questions & Answers - Learning Mode

Physics Interview Questions & Answers - Learning Mode

The dictionary definition of physics is ?the study of matter, energy, and the interaction between them?, but what that really means is that physics is about asking fundamental questions and trying to answer them by observing and experimenting. Physics (from Ancient Greek: φυσική (ἐπιστήμη) phusikḗ (epistḗmē) "knowledge of nature", from φύσις ph?"nature") is the natural science that involves the study of matter and its motion through space and time, along with related concepts such as energy and force.

Try Physics Interview Questions & Answers - Exam Mode

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Physics Interview Questions & Answers - Learning Mode
Try Physics Interview Questions & Answers - Exam Mode
Question: What is the 'Law of Machines'?

Answer: Machines which are used to lift a load are governed by the "Law of machines", which states that the effort to be applied on the machine (p) is related to the weight (w) which it can lift as -
p = mw + c
Where m and c are positive constants which are characteristics of the machine. Source:
Question: What is moment of inertia?

Answer: Moment of inertia is the term used to measure or quantify the amount of mass located at an object's extremities. For example if all the mass of an object was located in a small compact size (like a lead ball) its moment of inertia would be small compared to the same amount of mass shaped into a dumbbell. Because a dumbbell has most of its mass located farther from its center. But there is a "qualification" here. Moment of inertia is calculated relative to a hypothetical spin axis. Once you c Source:
Question: How many pounds does one gallon of water weigh?

Answer: One wine measure or US gallon of water weighs 8.34 pounds. An Imperial Gallon is ten pounds of water at 62F and 30 inches of mercury air pressure.
At 60F. The density of water (and any other liquid) is dependent on temperature. So a gallon of boiling water weighs less (8.00 pounds) than a gallon of water at 60F.

So fill up your car first thing in the morning when it should be the coolest, you'll get more pounds of gasoline.

Except that most vehicle fuels are stored undergrou Source:
Question: Is negative mass antimatter?

Answer: No. There is really no such thing as negative mass. Even antimatter has mass, which is always a positive (that is, greater-than-zero) quantity.

There is, however, the concept of effective mass or apparent mass, which can be negative. When an object is submerged in water, its apparent weight is reduced by an amount equivalent to the weight of water it displaces. For example, if a 10-pound rock is dropped into a bucket of water and displaces one pound of water, the effective weight of the r Source:
Question: How does laser printer works?

Answer: When a text or image is entered into the CPU, it produces a series of varying voltages. This controls a LED (light emitting diode) in the printer. This emits flashes of laser, when it falls on a charged photo conducting drum. The area corresponds the text or image will either be neutralized or oppositely charged. A toner which has the same charge as the background is sprayed onto it. It only sticks to the text or image and is repelled by the background. A fresh paper is now pressed onto the tone Source:
Question: What is density?

Answer: Density is a physical characteristic, and is a measure of mass per unit of volume of a material or substance. It is a measurement of the amount of matter in a given volume of something.
The higher an object's density, the higher it?s mass per unit of volume. The average density of an object equals its total mass divided by its total volume. A denser object (such as iron) will have less volume than an equal mass of some less dense substance (such as water). Source:
Question: What seven colors appear to be white when mixed together?

Answer: Red, orange, yellow, green, blue, indigo and violet. Though with the human eye, only red, green and blue are needed for light to appear white. Source:
Question: Give one advantage of a scanning electron microscope over a transmission electron microscope?

Answer: The SEM has become more popular than the TEM as it can produce images of high resolution, greater clarity and three dimensional qualities and requires less sample preparation Source:
Question: How is Specific Gravity defined?

Answer: Specific Gravity, SG, is a unit less quantity that gives the scientist or engineers an idea of how dense a substance is compared to water. The density of water, which is one kilogram per liter (at 4 degrees C), is assigned a SG of 1.000. If a substance is denser than water, it will have a SG greater than 1.000; if it is less dense than water, its S.G. will be a value less than 1.000 (but greater than zero). Let's say a substance has a density of 2.5 kilograms per liter. That means that its S Source:
Question: Does a soccer ball go faster in the air on a cold or hot day?

Answer: On a hot day, the air molecules have more kinetic energy - they move around more freely. They will move out of the way of the soccer ball that is moving through them more easily when the air is warm. In physics we might say that the warmer air is more susceptible to shear force than cooler air. The warmer air will "part" more easily to let the ball pass through. Source:
Question: What is different between secondary electron image and back scattered electron image?

Answer: Secondary electron images show topography of a sample. Back scattered electron images show difference in composition - or more exactly, difference in atomic number over a sample. Source:
Question: Will a DC motor actually produce voltage if it is spun in reverse?

Answer: It'll produce voltage if you spin it forwards, too. The only difference between a DC motor and a DC generator is what you use it for.

A long time ago, cars had DC generators on them instead of AC alternators. When you replaced a generator, you had to "polarize" it so it would make electricity. You hooked it up to your battery and let it run, as a motor, for a few seconds. Don't try that with an alternator because you'll break it.

If you're looking for a neat little Source:
Question: Why does heat cause matter to expand?

Answer: Water contracts as it cools, like all other liquids, until it reaches a temperature of about 4 degrees Celsius, at which point it expands and begins to form into crystals, expanding approximately 9 percent. BIO: Source:
Question: What is the difference between Free Electron Theory and Band Theory of solids?

Answer: Free Electron Theory:

This theory tells that, metals conduct electricity because of the presence of free electrons in it. The outermost shells of metal atoms will be loosely bound with their nucleus. So the electrons in it are free to move anywhere in the solid. These electrons are called free electrons and they are responsible for the conduction of electricity. Source:
Question: What two properties of electromagnetic waves are used to attach info to radio signals?

Answer: By varying the amplitude of a radio wave, you can encode information. That is how AM -radio works. By varying the frequency (and hence its wavelength) of a radio wave, you can also encode information. That is how FM radio works.

A good graphical explanation is given at Source:
Question: How can light be defined in simplest form?

Answer: The common definition of 'light' (visible) is electromagnetic radiation visible to the human eye. It is only a small part of what is known as the 'electromagnetic spectrum' - which is the range of wavelengths of all possible electromagnetic radiation. Source:
Question: What would happen if a disk one light second in circumference were to spin at 60 RPM?

Answer: 60 revolutions per minute is one revolution per second.

1 light second is the distance light travels in one second.

What this means is that points on this hypothetical disk's perimeter would need to travel at the speed of light to satisfy your conditions. This cannot happen for anything that has mass.

Bottom line: a disk this size could not spin at this speed. Source:
Question: Does weight affect how far you jump?

Answer: For the same leg strength / jumping technique, weight affects how far one can jump.

Acceleration = Force / Mass

With more mass, you cannot accelerate yourself as much when you jump with the same force. Imagine trying to jump with a small backpack full of sand strapped to your back. Your strength hasn't changed. That is, the amount of force you can deliver hasn't changed, but your mass has. You can't jump as high. Source:
Question: What are Newton's laws of motion?

Answer: . A body at rest will remain at rest and one in motion will remain in motion, until and unless acted upon by an external force. (Law of inertia)

2. The rate of change of momentum of a body is proportional to the resultant force acting on the body in the same direction as its motion. (F = ma)

3. For every action there is an equal an opposite reaction.

Note: These laws apply only at speeds not approaching the speed of light and do not apply to sub-atomic particles. Source:
Question: What are isotopes?

Answer: An atom of an element that has a different number of neutrons in its nucleus to other atoms of the element Source:

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Latest 20 Questions
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