POST UTME GREENFIELD UNIVERSITY 2017 Physics | Objective

Practice these randomly selected questions to test your readiness.

Question 1
A parallel plate capacitor consists of two plates, each of area 0.04 m^2, separated by a dis\tance of 0.02 m. The capaci\tance of the capacitor is 8 nF. If a potential difference of 10 V is applied across the plates, calculate the energy stored in the capacitor.
A. 0.16 J
B. 0.32 J
C. 0.64 J
D. 1.28 J
Question 2
A radioactive sample has an initial activity of 100 Bq. After 2 hours, the activity decreases to 50 Bq. What is the half-life of the sample?
A. 1 hour
B. 2 hours
C. 3 hours
D. 4 hours
Question 3
A wave of frequency $f$ and wavelength $\lambda$ is traveling through a medium with a speed $v$. If the wave's amplitude is doubled, what is the new intensity $I'$?
A. 4I
B. 2I
C. I
D. \frac{1}{4}I
Question 4
A heat engine operates between two temperatures $T_1$ and $T_2$, where $T_1 > T_2$. The engine absorbs $Q_1$ amount of heat from the high-temperature reservoir and rejects $Q_2$ amount of heat to the low-temperature reservoir. Assuming the engine is reversible, find the efficiency $\eta$ in terms of $Q_1$ and $Q_2$.
A. \eta = \frac{Q_1 - Q_2}{Q_1}
B. \eta = 1 - \frac{Q_2}{Q_1}
C. \eta = \frac{Q_2}{Q_1}
D. \eta = \frac{Q_1 + Q_2}{Q_1}
Question 5
A 100 W light bulb is connected to a 220 V power source. What is the current flowing through the bulb?
A. 0.45 A
B. 0.9 A
C. 1.8 A
D. 4.5 A
Question 6
A heat engine operates between a high-temperature reservoir at 500 K and a low-temperature reservoir at 300 K. What is the maximum efficiency?
A. 0.25
B. 0.30
C. 0.35
D. 0.40
Question 7
A body is in equilibrium under the action of two forces, one of magnitude 10 N and the other of magnitude 20 N. If the angle between the forces is 60°, determine the magnitude of the resul\tant force.
A. 10 N
B. 20 N
C. 30 N
D. 40 N
Question 8
A vector A has a magnitude of 5 units and makes an angle of 60° with the x-axis. What is the x-component of vector A?
A. 2.5
B. 4
C. 5
D. 7.5
Question 9
A parallel plate capacitor has a capaci\tance of $C = 2\,\mu\text{F}$ and is charged to a potential difference of $V = 10\,\text{V}$. If the dis\tance between the plates is doubled, what is the new capaci\tance $C'$?
A. 4\,\mu\text{F}
B. 2\,\mu\text{F}
C. 1\,\mu\text{F}
D. 0.5\,\mu\text{F}
Question 10
A particle of mass $m$ is attached to a spring with spring cons\tant $k$. The particle is displaced from its equilibrium position by a dis\tance $x_0$ and released from rest. Assuming the motion is simple harmonic, find the angular frequency $omega$ in terms of $k$ and $m$.
A. \omega = \frac{k}{m}
B. \omega = \sqrt{\frac{k}{m}}
C. \omega = \frac{m}{k}
D. \omega = \frac{1}{\sqrt{km}}
Question 11
A block of mass $M$ and density $\rho$ is floating in a fluid of density $\rho_f$. If the block is displaced by a dis\tance $x$ from its equilibrium position, what is the magnitude of the restoring force acting on it?
A. \frac{\rho V g x}{\rho_f}
B. \frac{\rho V g x}{\rho}
C. \frac{\rho_f V g x}{\rho}
D. \frac{\rho V g x}{\rho V}
Question 12
A 10 Ω resistor is connected in series with a 20 Ω resistor and a 30 Ω resistor. What is the total resis\tance?
A. 40 Ω
B. 50 Ω
C. 60 Ω
D. 70 Ω
Question 13
A particle of mass $m$ is moving in a straight line with an initial velocity $v_0$ and is subjected to a cons\tant acceleration $a$. If the particle's velocity after time $t$ is given by $v = v_0 + at$, what is the particle's position after time $t$?
A. \frac{1}{2}at^2 + v_0t
B. v_0t + at
C. \frac{1}{2}v_0t^2 + at
D. \frac{1}{2}at^2 - v_0t
Question 14
A particle of mass $m$ and charge $q$ is moving in a circular path of radius $R$ in a uniform magnetic field of strength $B$. If the particle's velocity is $v$, what is the magnitude of the magnetic force acting on it?
A. \frac{mv^2}{R}
B. \frac{mv^2}{2R}
C. \frac{mv^2}{4R}
D. \frac{mv^2}{8R}
Question 15
A particle of mass $m$ is moving in a circular path of radius $r$ with a cons\tant speed $v$. The particle is subjected to a centripetal force $F_c$ given by $F_c = \frac{mv^2}{r}$. If the particle's speed is doubled to $2v$, what is the new centripetal force $F_c'$?
A. \frac{2mv^2}{r}
B. \frac{4mv^2}{r}
C. \frac{mv^2}{2r}
D. \frac{mv^2}{4r}

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