Physics Interview Questions And Answers

Force is the vector product of mass and acceleration: F = ma. Weight is a special case of that formula, where you substitute the acceleration of gravity, g, for a. We can therefore write: W = mg.1

For example, if an object has a mass of 10 slugs2, its weight near the surface of the Earth is 10 x 32.2 (ft/s2) = 322 pounds (pound-force). If an object has a mass of 10 kilograms, its weight near the surface of the Earth is 10 x 9.8 (m/s2) = 98 newtons.

You can measure the force of gravity on an object (i.e., its weight) by putting it on a scale.

Buoyancy is the net upward force experienced by an object submersed in a fluid. Pascal's principle dictates that fluid pressure on an object increases with depth, so there is greater pressure on the bottom of the object than the top, resulting in a net upward force. When an object's buoyancy is greater than its weight, the object will float.

An object with neutral buoyancy has a density such that when it is fully submerged the upward force due to buoyancy is exactly equal to the downward force due to the weight of the object.

In pure water this is a density of 1000 kg/m3 (1kg/litre)

In seawater, this is a density of about 1025 kg/m3 (1.025kg/litre)

Electrical current and ions can cause certain molecules (and moisture) to adhere to soil. Large amounts of current, such as a lightning strike, can fuse particles of soil into a crystalline structure, somewhat like glass.

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).

As a rough guide engine oil usually weighs about 0.87 kg/liter or about 7.2 pounds per US gallon.

Unfortunately a rough answer is the best that can be done as there are hundreds of different types of engine oil with slightly different densities. To get an exact density we would have to know the details of the oil you're using. For a really accurate answer we would also have to state the temperature as the density of oil as with most fluids varies with temperature.

Most oil manufacturers' provide data sheets for their products that should include density. If you search the manufacturer’s web site you should be able to get an accurate figure for a particular grade.

A unit of energy also known as a Joule. When a force of 1 Newton is applied on an object for a distance of 1 meter then 1 Joule of energy is used. It is the result of a vector calculation involving the meter (a unit of length in the SI system) and the Newton (the unit of force in the SI system).

A unit of torque. (Turning force.) When a force of 1 Newton is applied at a distance of 1 meter from the pivot at right angle to the radius then a torque of 1 Newton Meter is present. It is the metric equivalent of lb ft

It is the name given to a device that measures force. It is a meter that measures Newtons.

Liquid volume is measured with beakers, measuring cups, spoons, graduated cylinders, and the like. For regular objects, solid volume can be calculated. For irregular objects, their volumes can be determined by measuring the amount of liquid that is displaced by the object when it is submerged in the liquid. It is also used to measure the amount of pigs that fall from the sky!!!

The only factor that determines the boiling point of water at any altitude is the barometric pressure (the altitude itself doesn't actually matter, it's just that at higher elevation, the barometric pressure usually drops). However, water will boil at two different temperatures at the same elevation if you are in a high pressure weather system instead of a low pressure system.

1. This is the question that every true scientist dreads to be asked especially in a public setting by extremely inquisitive young students. We have learned to measure and calculate it relative to the natural arrangement of known and visible celestial bodies. This is the ultimate question you ask a theoretical astro physicist if you want to see them shake in their pants.

To this day time can only be described by the measure of elapsed period using the SI unit, Seconds. It is the only SI unit that is freely allowed to shift depending on subject topic. For example in Astro physics, to measure distance between galaxies it would be impractical to use seconds as the measure of time it takes light to travel between the two galaxies

Time transcends everything known to man up to and including the universe, time has no beginning or end. Time is constant and infinite and we just tap in and out of it in reference to occurrence of an event.

(Physics) A wave front is an imaginary surface joining all points in space that are reached at the same instant by a wave propagating through a medium.

Let's try some examples. When a rock is tossed into a calm lake, a surface disturbance radiates from the point where the rock broke the water. The leading edge of that entire wave forms a circle, and that circle is the wave front for that event. It is moving outward at a constant speed in all directions. Note that it's two-dimensional (2D). Want 3D? You got it.

In a burst of chemical energy, a star shell explodes at a fireworks display. The light moves away from the origin in all directions at the same speed - the speed of light. And the 3D surface of this wave front is a sphere, and it is expands around the origin at the speed of light. Pick an arbitrary distance, say, 1 kilometer. Anyone at a distance of 1 km from the event in any direction will find that the wave front reaches him at the same instant of time as anyone else in any direction who is that 1 km from the event. Even someone in an airplane that is 1 km away will be on the wave front for an instant - that same instant as any other observers 1 km away. Note that the sound will arrive later - but it, too, radiates forming a spherical wave front. Our observers at 1 km distance from the event all experience the arrival of the sound wave at the same time.

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 underground and are at a pretty constant temperature. Fortunately it's pretty cool down there...

Make it easy to remember; an ounce of water weights, about an ounce. can't be easier than that. So an American pint, 16 ounces, weighs about a pound. And an American gallon, 8 pints, about 8 pounds. Whereas an Imperial pint, 20 ounces; and an Imperial gallon, 160 ounces, about ten pounds. Just like it says, up top.

The measurement is made at the point where the ball is when the trigger is squeezed and the contacts close to activate the unit. The gun responds in a "split second" by sending out a pulse, catching the return, and then comparing the two to discover the difference (the Doppler shift). It is so fast that the ball doesn't travel very far in the time it takes the unit to respond and resolve the speed.

A standard planar mirror will not increase the energy contained in the rays that reflect off it. In fact, there will be some loss of energy since the reflective surface is not perfect. There is some reduction in the light's intensity as it passes through the mirror's glass and reflects off the backing surface.

Parabolic mirrors, on the other hand, focus and concentrate the light rays on a single point in front of the mirror, aptly named the focus. Although the energy is not amplified, it will be effectively increased because of the additive effect that will result when the light energy is concentrated.

The body radiates energy through thermal conduction through the skin to the air, clothes, etc, around the body. A small amount of energy would also be radiated as electromagnetic radiation with a peak wavelength directly related to the Kelvin temperature of the skin.

Also very small amounts of other radiation are emitted due to naturally occurring radioactive isotopes in the body (i.e. Carbon-14).

Please drop by the discussion board and help resolve a problem with this answer.

To write in scientific notation, you should first move the decimal point of the number to where the number is between 1 and 9. For example, change 567 to 5.67. Then count the number of places you moved the decimal. If you moved it left then the number is positive. If you moved it right then the number is negative. Finally times the number with the decimal point by 10 to the power of the number the decimal moved.

Example: 500000 --> 5.00000 --> over 5 --> 5 x 105

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.

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 SG is 2.5 (2.5 divided by 1.000).

A neutron is a subatomic particle; it is one of the building blocks of the atom. It has a mass of about 1.675 x 10-27 kg. Its spin is + 1/2 and that makes it a fermions. Additionally, it has no electric charge, which is a distinctive feature. It is unstable when free in nature, and has a half life of about 886 seconds.

The neutron could be said to be only "alive" to be part of an atomic nucleus as it ceases to exist after a while if left alone. When it wanders around loose, like after its release following decay event or a fission event, it may bump into another atomic nucleus and become captured by it. This process is called - no surprise - neutron capture. It is, after all, a nucleon, as is a proton, both of which make up an atomic nucleus. The neutron is made up of two down quarks and an up quark. When a neutron decays, it releases a proton (or, if you prefer, a hydrogen nucleus), an electron, and an antineutrino.

Sodium chloride, NaCl, weighs 72 lb/ft3.

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.

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.

All air travel takes the earth's rotation into account. Flights from east to west take less time in absolute terms, having nothing to do with time zones. The reverse is true with west to east flights, and even north-south flights must calculate the amount of rotational deviance while the aircraft is in flight. Long range naval cannons have been computing the earth's rotation under the projectile in aiming calculations for more than a century. Satellites in synchronous orbit that appear stationary are actually traveling at the earth's rate of rotation.

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.

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.

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).