POST UTME UNIBEN 2018 Physics | Objective

Practice these randomly selected questions to test your readiness.

Question 1
A magnetic field of strength B is directed perp\endicular to a current-carrying wire of length L. If the current in the wire is I, what is the force on the wire?
A. BI
B. BL
C. BI^2
D. BL^2
Question 2
A radioactive sample has a half-life of $t_{1/2}$. If the initial activity is $A_0$, what is the activity after a time $t$?
A. A_0 e^{-\lambda t}
B. A_0 e^{\lambda t}
C. A_0 + \lambda t
D. A_0 - \lambda t
Question 3
A quantum particle is confined to a one-dimensional box of length $L$. If the particle has a mass of $m$ and a energy of $E$, what is the wavelength of the particle?
A. \frac{2\pi\hbar}{\sqrt{2mE}}
B. \frac{\pi\hbar}{\sqrt{2mE}}
C. \frac{2\pi\hbar}{\sqrt{mE}}
D. \frac{\pi\hbar}{\sqrt{mE}}
Question 4
A particle of mass 2 kg is moving in a circular path of radius 3 m with a cons\tant speed of 4 m/s. If the particle is subjected to a centripetal acceleration of 2 m/s^2, what is the magnitude of the net force acting on the particle?
A. 8 N
B. 10 N
C. 12 N
D. 16 N
Question 5
A particle of mass 0.5 kg is moving in a circular path of radius 2 m with a cons\tant speed of 4 m/s. If the particle is subjected to a centripetal force of 10 N, calculate the time it takes for the particle to complete one revolution.
A. 2 seconds
B. 4 seconds
C. 6 seconds
D. 8 seconds
Question 6
A 10 kg block is attached to a horizontal spring with a force cons\tant of 100 N/m. If the block is displaced by 2 m from its equilibrium position and released, calculate the maximum speed of the block.
A. 2 m/s
B. 4 m/s
C. 6 m/s
D. 8 m/s
Question 7
A charged particle is moving through a region with a uniform magnetic field. If the particle has a charge of $q$ and a velocity of $v$, what is the magnitude of the force exerted on the particle?
A. qvB
B. \frac{mv^2}{r}
C. \frac{mv^2}{r^2}
D. \frac{mv^2}{r^3}
Question 8
A 240 V, 50 Hz AC supply is connected to a circuit containing a 10 Ω resistor and a 20 Ω inductor in series. If the current in the circuit is 2 A, what is the power factor of the circuit?
A. 0.5
B. 0.6
C. 0.7
D. 0.8
Question 9
A magnetic field is produced by a current-carrying wire. If the current is doubled, what happens to the magnetic field?
A. Increases by a factor of 2
B. Increases by a factor of 4
C. Increases by a factor of 8
D. Remains the same
Question 10
A magnetic field of strength 0.5 T is applied to a current-carrying wire of length 2 m. If the current is 5 A, what is the magnitude of the force acting on the wire?
A. 1.25 N
B. 1.5 N
C. 1.75 N
D. 2 N
Question 11
A ray of light passes from air into a glass of re\fractive index $n$. If the angle of incidence is $\theta_i$ and the angle of re\fraction is $\theta_r$, what is the value of the angle of re\fraction?
A. \sin \theta_i
B. \cos \theta_i
C. \tan \theta_i
D. \frac{n_1}{n_2} \sin \theta_i
Question 12
A circuit consists of a resistor, an inductor, and a capacitor connected in series. If the frequency of the AC source is increased, what happens to the impedance of the circuit?
A. Increases
B. Decreases
C. Remains the same
D. Increases and then decreases
Question 13
A particle of mass $m$ is moving in a circular orbit of radius $r$ under the influence of a central force given by $F(r) = -\frac{k}{r^2}$. If the particle's speed is $v$, what is its angular momentum?
A. mvr
B. mvr^2
C. mv^2r
D. mv^2/r
Question 14
A wave of wavelength $lambda$ and frequency $f$ is traveling through a medium with speed $v$. What is the magnitude of the wave's momentum?
A. \( \frac{hf}{c} \)
B. \( \frac{hf}{v} \)
C. \( \frac{h}{lambda} \)
D. \( \frac{h}{v} \)
Question 15
A particle of mass $m$ is moving in a circular path of radius $r$ with a cons\tant speed $v$. If the particle experiences a centripetal force $F_c = \frac{mv^2}{r}$, what is the magnitude of the acceleration of the particle?
A. \frac{v^2}{r}
B. \frac{mv^2}{r}
C. \frac{2mv^2}{r}
D. \frac{3mv^2}{r}

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