If a particle and antiparticle are in the appropriate quantum states, then they can annihilate each other and produce other particles.

If denotes the quantum state of a particle ( n ) with momentum p, spin J whose component in the z-direction is σ, then one has

If the path of the particle or centre of mass of the rigid body passes through the given origin, its angular momentum is zero.

If we define r < sub > i </ sub > as the displacement of particle i from the center of mass, and v < sub > i </ sub > as the velocity of particle i with respect to the center of mass, then we have

If a particle of the beam crosses this surface, there will be some kind of interaction.

If we think of the atoms as impenetrable steel discs and the impinging particle as a bullet of negligible diameter, this ratio is the probability that the bullet will strike a steel disc, i. e., that the atomic projectile will be stopped by the foil.

If this acceleration is multiplied by the particle mass, the leading term is the centripetal force and the negative of the second term related to angular acceleration is sometimes called the Euler force.

If the depletion layer is large enough to catch the whole shower or to stop a heavy particle, a fairly accurate measurement of the particle ’ s energy can be made, simply by measuring the charge conducted and without the complexity of a magnetic spectrometer, etc.

If an elementary particle truly has no substructure, then it is one of the basic building blocks of the universe from which all other particles are made.

If the entire volume of the observable universe ( taken to be 3 × 10 < sup > 80 </ sup > m < sup > 3 </ sup >) were packed solid with fine dust particles about 1. 5 micrometres in size, then the number of different ways of ordering these particles ( that is, assigning the number 1 to one particle, then the number 2 to another particle, and so on until all particles are numbered ) would be approximately one googolplex.

If the particles are indistinguishable, this is impossible by definition ; either particle can be in either state.

If the particles are bosons, they occupy a totally symmetric state, which is symmetric under the exchange of any two particle labels:

If a particle of charge q moves with velocity v in the presence of an electric field E and a magnetic field B, then it will experience a force

If a force is applied to a particle for a time interval, the momentum of the particle changes by an amount

If the particle is moving at speed in the first frame of reference, in the second it is moving at speed

If a charged particle moves in an electromagnetic field, its kinematic momentum is not conserved.

If, e. g., u is the speed of a particle, then the straightforward notation for its velocity is u, < u > u </ u >, or.

If the photon energy is absorbed, some of the energy liberates the electron from the atom, and the rest contributes to the electron's kinetic energy as a free particle.

If the particle is in an eigenstate of position, then its momentum is completely unknown.

If the spin of a particle has a positive projection on its direction of motion then it is called left-handed ; otherwise, it is right-handed.

If Alice has a particle which is entangled with a particle owned by Bob, and Bob teleports it to Carol, then afterwards, Alice's particle is entangled with Carol's.

If the circumstances are faced frankly it is not reasonable to expect this to be true.

If his dancers are sometimes made to look as if they might be creatures from Mars, this is consistent with his intention of placing them in the orbit of another world, a world in which they are freed of their pedestrian identities.

If a work is divided into several large segments, a last-minute drawing of random numbers may determine the order of the segments for any particular performance.

If they avoid the use of the pungent, outlawed four-letter word it is because it is taboo ; ;

If Wilhelm Reich is the Moses who has led them out of the Egypt of sexual slavery, Dylan Thomas is the poet who offers them the Dionysian dialectic of justification for their indulgence in liquor, marijuana, sex, and jazz.

If he is the child of nothingness, if he is the predestined victim of an age of atomic wars, then he will consult only his own organic needs and go beyond good and evil.

If it is an honest feeling, then why should she not yield to it??

If he thus achieves a lyrical, dreamlike, drugged intensity, he pays the price for his indulgence by producing work -- Allen Ginsberg's `` Howl '' is a striking example of this tendency -- that is disoriented, Dionysian but without depth and without Apollonian control.

If love reflects the nature of man, as Ortega Y Gasset believes, if the person in love betrays decisively what he is by his behavior in love, then the writers of the beat generation are creating a new literary genre.

If he is good, he may not be legal ; ;

If the man on the sidewalk is surprised at this question, it has served as an exclamation.

If the existent form is to be retained new factors that reinforce it must be introduced into the situation.

If we remove ourselves for a moment from our time and our infatuation with mental disease, isn't there something absurd about a hero in a novel who is defeated by his infantile neurosis??

If many of the characters in contemporary novels appear to be the bloodless relations of characters in a case history it is because the novelist is often forgetful today that those things that we call character manifest themselves in surface behavior, that the ego is still the executive agency of personality, and that all we know of personality must be discerned through the ego.

If he is a traditionalist, he is an eclectic traditionalist.

If our sincerity is granted, and it is granted, the discrepancy can only be explained by the fact that we have come to believe hearsay and legend about ourselves in preference to an understanding gained by earnest self-examination.

If to be innocent is to be helpless, then I had been -- as are we all -- helpless at the start.

If an evacuated glass tube is equipped with two electrodes and a voltage is applied, the glass opposite of the negative electrode is observed to glow, due to electrons emitted from and travelling perpendicular to the cathode ( the electrode connected to the negative terminal of the voltage supply ).

If, as is most common, this flow is carried by electrons, they will be travelling in the opposite direction.

The Simpsons episode " Catch ' Em If You Can ", aired 25 April 2004, alluded to the snob appeal of The Economist in an exchange between Homer and Marge Simpson while they are travelling first-class aboard an airplane:

If travelling independently without using an agency, since 2008 it is required to apply for a special borderzone permit in order to be allowed into the area.

If holders of a permit to travel are asked to present their ticket by an inspector, they will be asked where they are travelling to and issued with the appropriate ticket and will be charged the difference between the balance already paid, as stated on the permit and the full cost of the ticket for their journey.

If a saint did a lot of travelling then the bones of his feet may be prized.

If a certain " Chong Kinley " is from Chozom village in the Paro valley, she is called " Paro Kinley " when she is travelling outside the valley.

If the pair divorces for some reason then the birds will disperse, with females travelling further than males to establish new territories.

If travelling east from the Blue Mountains, access is best obtained by the Great Western Highway.

If travelling on a route outside Zone 1 via Willesden Junction, the fares are £ 3. 50 and £ 1. 30 respectively, which can be charged correctly if the Oyster card is validated at the pink validator when changing trains at Willesden Junction.

If travelling medium distances, ( about 30 – 100 km ), a special dragline carrier can be brought in to transport the dragline.

If other ants find such a path, they are likely not to keep travelling at random, but to instead follow the trail, returning and reinforcing it if they eventually find food ( see Ant communication ).

If the Uber car is travelling at a speed greater than 11 mph, the price is calculated on a distance basis.

If you are travelling from Vientiane you can either take VIP buses or local buses.

If the ball hits the batsman either on the full or immediately after bouncing, the umpire assumes that the ball is travelling straight on, ignoring any spin, swing or other hard to predict movement that may have changed the direction of the ball if it had not hit the batsman.

If the train is travelling at speed, this may be too late to stop it before the point of collision, therefore a second transmitter may be placed on the approach to the signal that applies the brakes on trains going too quickly to stop at the signal, and this is positioned to safely stop trains approaching at up to 75 mph ( 120 km / h ).

If it is travelling above the preset trigger speed, one or two photographs are taken ( depending on the device's setting, which generally depends on the requirements of the local jurisdiction ).

If she met travelling musicians on the road she would dismount and dance to a jig or hornpipe.

If travelling by coach passengers will often be expected to place their own luggage in the hold, before boarding.

If a pilot is flying a leg of 120 miles and finds after travelling 60 miles that they are two miles to the right of track then a correction of 4 ° to the left ( 2 ° to fly parallel to the intended track and another 2 ° to bring them to their target ) will bring them to their destination.

If a player or an official accepts from club, association, or federation an amount exceeding what is strictly necessary for travelling and hotel expenses, such an amount will be regarded as profit.

If travelling via London it is often necessary to change stations: a journey from Norwich to Cardiff would require a transfer from London Liverpool Street to London Paddington station via the London Underground.

If found to be travelling without a ticket, then they are required to pay an increased fare of € 40.

If travelling by road one enters the Roseland at the bottom of Tregony Hill by either driving up Reskivers Hill to take the road to St. Mawes and Gerrans, or by taking the lower road to Ruan Lanihorne.