Phenomenal Physics! Trivia Quiz

Answer: Hooke's Law

Hooke's law 'F = -kx' shows that the extension is proportional to the force applied but the force acts in the opposite direction to the extension. In an oscillating mass-spring system, if the extension was downward (stretching) the spring force would be acting upward. If the extension was taking place upward (compression) the spring force would be acting downward. Hooke's law only applies if the elastic limit of the spring isn't surpassed. If the elastic limit is passed, the spring will not return to its original form but will be disfigured.

The equation also shows the constant 'k' which is known as the spring constant. This value depends on the spring you use and the unit of the spring constant is Nm^-1 (Newtons per metre).

Answer: true

The equation 'F = ma' shows you that force is directly proportional to mass and that force is also directly proportional to acceleration. You can simply put some numbers into the equation to check the answer to this question out.

If an object of mass 10kg was accelerating at 10ms^-2 then the force would be:

F = ma
F = 10 x 10
F = 100N (Newtons)

If the mass of the object is then doubled and the acceleration halved you have a new equation for force:

F = ma
F = 20 x 5
F = 100N

The two values, as you can see, are both the same at 100N.

Answer: Force per unit area

This is shown algebraically as 'p = F/a' and this is used to derive the unit of pressure which is Nm^-2 (Newton per metre squared) or the Pascal, 'P'. To expand on the concept slightly, the force applied is required to be perpendicular to the surface of the area. If the force is applied at an angle, trigonometry and the vertical component of the applied force can be used to obtain the value of the perpendicular force.

Pressure can also be seen in a gas equation known as the 'Ideal Gas Equation'. The equation is pV = nRT, where p = pressure, V = volume, n = number of moles, R = molar gas constant and T = temperature.

Answer: Resistance

Ohm's Law states that "the current flowing between two points is directly proportional to the potential difference across those points"*. This has some limitations however, as the temperature of the conductor must stay constant (which it doesn't). Thus, as the current flowing increases, the potential difference (voltage) will increase in direct proportion and the resistance of the conductor will remain the same. The only problem is that as the value of the current flowing increases, the temperature within the conductor also increases and by extension, the resistance of the conductor increases. When a conductor no longer follows Ohm's law, it is said to be non-Ohmic. There are conductors that do not follow Ohm's law and they include various diodes that control the direction of current flow.

*A standard textbook definition.

Answer: Centripetal force

The equation F = (mv^2)/r shows that force (centripetal) is equal to the product of the mass of an object and its velocity squared all divided by the radius of the circle (orbital path). When working with calculations related to circular motion, one must work in radians rather than in degrees. There is even an equation that shows the conversion of degrees into radians and that is 360 degrees = 2*pi radians. As you can see, there are 2*pi radians in a full circle and you will see 2*pi popping up quite frequently in physics. One equation where it is noticeable is the relationship between angular velocity* (omega) and time period (T). The equation is T = (2*pi)/(omega) and as you can see the important 2*pi is present.

*Angular velocity is the angle turned about a point per second and it has the units radians per second (rad s^-1).

Answer: Photoelectric Effect

There is no doubt that Albert Einstein's most famous equation is E = mc^2. The equation has such striking brevity and compelling simplicity (that is before you start to use it!). However, Einstein won his Nobel Prize in the fascinating field of physics for his work on the photoelectric effect.

The equation E = phi + Ek(max) describes the behaviour of photon-electron interaction. E stands for the energy of an incident photon and the energy of a photon is dependent upon its frequency (E = Planck's constant x frequency) such that a greater photon frequency results in a greater photon energy.

Back now to the equation and the Greek letter phi which represents the work function which is the minimum energy needed to excite an electron (or photoelectron after its interaction with a photon) such that the electron leaves the surface of an object. Furthermore, phi = hf0, where h = Planck's constant. This suggests that the work function is dependent upon the threshold (f0) frequency needed to excite an electron in a particular metal.

The final variable in the equation is Ek(max) which is the maximum kinetic energy of the emitted photoelectron. Thus, the equation is stating that the energy of an incident photon is equal to the sum of the work function of a metal and the maximum kinetic energy of the excited and emitted photoelectron.

Answer: Magnetic flux density

Yes, meet 'Bill' who has a friend called 'Bev'. Two of the equations of force in this field of physics are F = BIl and F = BeV where the letter B in both instances represents the magnetic flux density or the magnetic field strength. The letter 'I' in the 'Bill' equation is for current and the 'l' represents the length of a current carrying conductor in the magnetic field at a right angle.

The equation F = BeV can also be seen as F = BQV where 'Q' represents charge and 'e' is more specifically the charge of an electron. It all depends on the context as to which you use though they can often be used interchangeably. Finally, the letter V represents velocity (speed with a direction) which is an important difference between the two equations as it indicates that in the 'Bev' equation, the force is caused due to a moving charge.

Answer: Q = It

The SI unit of current (I) is the Ampere or Amp (A) and the SI unit of time is the second (s). Therefore, from the information that 1C = 1A.1s, one can gather that one Coulomb of charge is equal to 1 Amp of current flowing in one second. This shows that equations for physical phenomena can be derived from simply looking at their units.

However, as the units get more and more complex, the equations get harder and harder to derive.

Answer: Frequency

Frequency (f) isn't just applicable to waves but is used in electronics such as the frequencies involved with AC electricity supplies. Frequency is also used extensively in maths, particularly in the field of statistics.

The equation for wave speed (v) is wave speed = frequency x wavelength. Algebraically this can be seen as v = f x lambda.

Answer: GPE = mgh

Gravitational potential energy is the energy of an object of a particular mass due to its relative height. Essentially, the GPE of an object is the same as the work done to move the object's mass a certain distance. This can be shown algebraically:

Work done = Force x Distance (in direction of the force)
Force = mass x acceleration due to gravity
GPE = mass x acceleration due to gravity x height

So you can firstly put force into the GPE equation, GPE = force x height. As height is just a vertical distance, we can say that GPE = force x distance and subsequently, GPE = work done.

Thanks for playing the quiz and I hope you enjoyed!