Physics 2006 Jamb Examination
Physics 2006 Jamb Examination
Question 21
If the radius of the Earth is $6.4 \times 10^6 \; m$, the escape velocity of a satellite from the Earth is?
$g = 10 \; ms^{-2}$
$g = 10 \; ms^{-2}$
Escape velocity: $v = \sqrt{2gR} = \sqrt{2 \times 10 \times 6.4 \times 10^6} = \sqrt{1.28 \times 10^8} \approx 1.13 \times 10^4 \; ms^{-1}$.
Not clear enough?
Question 22
The component of vector $X$ along the direction of vector $Y$ is zero when
Component of $X$ along $Y$ is $|X| \cos \theta$. For it to be zero, $\theta = 90^{\circ}$, i.e., $X$ is perpendicular to $Y$.
Not clear enough?
Question 23
The correct unit of energy density is?
Energy density = $\dfrac{Energy}{Volume} = \dfrac{J}{m^3} = \dfrac{kg \, m^2 \, s^{-2}}{m^3} = kg \, m^{-1} \, s^{-2}$.
Not clear enough?
Question 24
I. Work done by load is always less than the work done by effort.
II. All machines are made of levers, pulleys, screws and gear wheels.
III. A fishing rod is a machine.
IV. Effort is always larger than load.
Which of statements above about machines are true?
II. All machines are made of levers, pulleys, screws and gear wheels.
III. A fishing rod is a machine.
IV. Effort is always larger than load.
Which of statements above about machines are true?
A fishing rod is a machine (III). Work output is always less than work input due to energy losses, so I is true. Correct statements: I and III.
Not clear enough?
Question 25
The energy associated with the emitted photon when a mercury atom changes from one state to another is $3.3 \, eV$. Calculate the frequency of the photon.
$e = 1.6 \times 10^{-19} C; \; h = 6.6 \times 10^{-34} Js$
$e = 1.6 \times 10^{-19} C; \; h = 6.6 \times 10^{-34} Js$
Energy $E = 3.3 \times 1.6 \times 10^{-19} = 5.28 \times 10^{-19} J$.
Frequency $f = \dfrac{E}{h} = \dfrac{5.28 \times 10^{-19}}{6.6 \times 10^{-34}} \approx 8.0 \times 10^{14} Hz$.
Frequency $f = \dfrac{E}{h} = \dfrac{5.28 \times 10^{-19}}{6.6 \times 10^{-34}} \approx 8.0 \times 10^{14} Hz$.
Not clear enough?
Question 26
The process through which free electrons leave the surface of hot metal is known as?
This process occurs when the thermal energy of the metal is sufficient to allow electrons to overcome the work function and escape from the surface.
Not clear enough?
Question 27
The battery connection that permits current to flow across a p-n junction is called?
Definition: A battery connection that allows current to flow across a p-n junction. Positive terminal to the p-type semiconductor and negative terminal to the n-type.Reduces the potential barrier, allowing charge carriers (holes and electrons) to move toward the junction and enabling current flow.
Not clear enough?
Question 28
One of the properties of gamma rays is that they are?
Neutral: Gamma rays are a form of electromagnetic radiation and carry no electric charge. Massive: Gamma rays are mass less photons. Positively/Negatively Charged: They do not have any charge, distinguishing them from particles like protons (positive) or electrons (negative)
Not clear enough?
Question 29
A radioactive element has a half life of 4 days. The fraction that has decayed in 16 days is?
\[ 16 \, \text{days} = 4 \, \text{half-lives}. \] \[ \text{The fraction left after 4 half-lives} = \left(\tfrac{1}{2}\right)^4 = \tfrac{1}{16}. \] \[ \text{Fraction that decayed} = 1 - \tfrac{1}{16} = \tfrac{15}{16}. \]
Not clear enough?
Question 30
The theory of electronic conduction in solids, which satisfactorily explains the properties of conductors, insulators and semi-conductors, is?
Band Theory: This theory describes the energy levels of electrons in solids as bands. It explains how the bands (valence and conduction bands) determine the electrical properties of materials.