POST UTME UNIBEN 2018 Physics | Objective

Practice these randomly selected questions to test your readiness.

Question 1
A convex lens of focal length 20 cm is placed in a beam of light. If the object dis\tance is 30 cm, calculate the image dis\tance.
A. 10 cm
B. 20 cm
C. 30 cm
D. 40 cm
Question 2
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 3
A particle of mass $m$ is moving in a circular orbit of radius $r$ with a speed $v$. If the particle is subjected to a uniform magnetic field of strength $B$, what is the magnitude of the magnetic force acting on the particle?
A. \( \frac{mv^2}{r} \)
B. \( \frac{mv^2}{r^2} \)
C. \( \frac{mv}{r} \)
D. \( \frac{mv^2}{r^3} \)
Question 4
A 6 V battery is connected in series with a 2 Ω resistor and a 4 Ω resistor. If the current in the circuit is 1 A, what is the voltage across the 2 Ω resistor?
A. 2 V
B. 3 V
C. 4 V
D. 5 V
Question 5
A 2 kg block of ice at 0°C is placed in a 10°C water bath. Assuming the specific heat capacity of ice is 2.05 kJ/kg·K and the specific heat capacity of water is 4.184 kJ/kg·K, calculate the time it takes for the ice to melt completely.
A. 10 minutes
B. 20 minutes
C. 30 minutes
D. 40 minutes
Question 6
A light ray passes through a prism of angle 30° and is re\fracted at an angle of 20°. If the angle of incidence is 40°, what is the angle of emergence?
A. 60°
B. 70°
C. 80°
D. 90°
Question 7
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 8
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 9
A thermodynamic system undergoes a process from state A to state B, where the temperature increases from 20°C to 40°C. If the heat capacity of the system is 100 J/K, what is the change in internal energy?
A. 2000 J
B. 3000 J
C. 4000 J
D. 5000 J
Question 10
A radioactive sample decays at a rate given by the equation $\frac{dN}{dt} = -\lambda N$, where $N$ is the number of nuclei and $\lambda$ is the decay cons\tant. If the initial number of nuclei is $N_0$ and the time elapsed is $t$, what is the number of nuclei remaining?
A. N_0 e^{-\lambda t}
B. N_0 e^{\lambda t}
C. N_0 + \lambda t
D. N_0 - \lambda t
Question 11
A parallel plate capacitor has a capaci\tance of C and is charged to a potential difference of V. If the dis\tance between the plates is increased by a factor of 2, what is the new capaci\tance?
A. C/2
B. C
C. 2C
D. 4C
Question 12
A particle of mass $m$ is confined to a one-dimensional box of length $L$. If the energy of the particle is $E$, what is the value of the wave number $k$?
A. \frac{\pi}{L}
B. \frac{2\pi}{L}
C. \frac{\sqrt{2mE}}{\hbar}
D. \frac{2\sqrt{2mE}}{\hbar}
Question 13
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 14
A 5 kg block is moving in a straight line with a cons\tant acceleration of 2 m/s^2. If the initial velocity is 4 m/s, calculate the time it takes for the block to reach a velocity of 8 m/s.
A. 2 seconds
B. 4 seconds
C. 6 seconds
D. 8 seconds
Question 15
A simple harmonic oscillator of mass $m$ and spring cons\tant $k$ is displaced from its equilibrium position by a dis\tance $x$. What is the magnitude of the force acting on the oscillator?
A. ( kx )
B. \( \frac{kx}{m} \)
C. \( \frac{kx^2}{m} \)
D. \( \frac{kx^3}{m} \)

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